MSI Observation Overview Document Author - Ann Harch, Cornell University, 9/26/01 Acknowledgements: The acquisition and archiving of this large data set were the result of intensive work by a relatively small group of people. Scott Murchie and myself, with assistance from Mark Robinson, Peter Thomas, Noam Izenberg and Jim Bell, were responsible for design of the MSI and NIS observations. Colin Peterson and Maureen Bell provided invaluable support in sequencing and software support during orbital operations. The ORBIT visualization software, crucial to the planning and execution of all of these sequences was created and built by Brian Carcich here at Cornell. Jonathan Joseph, also at Cornell, created and built the POINTS software that generated the shape model of Eros used by both the planning software and for science data analysis. Mark Robinson, Scott Murchie, Deborah Domingue, and Louise Prockter were essential to the data calibration efforts. The great task of archiving was accomplished primarily by Howard Taylor, Kopal Barnouin-Jha at APL, AND everyone mentioned above. This website was created and populated with the invaluable assistance of Gemma Carcich. Our team was guided and supported throughout bythe MSI/NIS Team Leader, Joseph Veverka. It goes without saying that none of this would have been possible without the skill and dedication of the NEAR JPL Navigation Team and the NEAR APL Operations, Engineering and Science Data Center Teams. *************************************1*************************************** 1.0 Introduction ***************************************************************************** The objective of this document is to provide an overview of the NEAR MSI observations. It is intended to be used as a companion document to the spreadsheets available in the eros and pre_eros subdirectories to present more detailed descriptions of observations in the context of the larger events they comprised. The information here is presented in time order from start of mission to end of mission and is divided into obvious chapters that represent the major observation events or orbital phases. Each chapter has a section which describes the historical background and one that talks about the detailed sequencing design. The historical background section provides some context for understanding why observations were planned and acquired. This may include information about spacecraft and mission events, as well as the orbital context. In the sequence design sections I try to explain more about how the detailed design of the observations attempted to satisfy the science requirements. For the orbital mission, the observations are sorted into catagories, and these observation types are described. Lists of individual observations that fall within each catagory are also given. Some limited information about NIS data is available here, mainly regarding the earth moon flyby activities and the pre-eros calibrations. Most of the NIS observations acquired in the post-orbit insertion period and high orbits were designed as cooperative observations with MSI. Pointing control often (but not always) resided the MSI sequences, and that is described here. More information about NIS is available in the NIS browse area. A word about the associated files. A complete list of the types of files available and the directory structure can be found in welcome.txt, eros_seq_archive.txt and pre_eros_seq_archive.txt files. Description and plot files are available for many of the observations and linked directly from the spreadsheets. There are references to many of these files in the main text of this document, but as an overview, here is what is available: Pre_Eros: -------- Imagelists - Imagelists exist only for the Mathilde flyby and the Earth Moon Flyby. They are NOT linked from anywhere on the spreadsheet, but can be found in the /pre_eros/mathilde subdirectory, and the /pre_eros/earthmoon_flyby/ subdirectory, respectively. Sequence Files - The STOL scripts for many of these sequences are linked from the Sequence Column. Summary text descriptions are available at the top of some of these. Detailed Description - Some individual text description files are available, linked from the Detailed Description column for some calibrations and the Earth Moon Flyby activities. Mathilde is described in this document in Chapter 3. Plots - IDL plots for the Earth Moon flyby and Orbit simulation s/w plots for the Mathilde Flyby are linked from the Predict columns and described in the text of this document. Orbital Info - text file overview of Mathilde trajectory linked from front page. Eros: ---- Imagelists - There is an imagelist available for EACH sequence week sequence starting with week 99347. There is also a special one for Eros Flyby in week 98357. These are NOT linked from the spreadsheet. Click on the week number in the Sequence column and it will take you to the subdirectory for that week. Sequence files - For each sequence there is a sequence file (xxxxx_final_sasf.txt) and a command expansion file for msi and nis (xxxxx.msi, xxxxx.nis). Like the imagelists, these can be accessed by going to the subdirectory for that week. (for example, /eros/00010 is the subdirectory for week starting 2000/00010) Description Files - Individual description files exist for certain complicated sequences or observation sub-types. Many are linked from the Detailed Description column. These are all text files and they are located in the ../eros/descript/ subdirectory. A complete list of these is found in the ../eros/descript/observation_key.txt file (linked from front page). Sorted Excel files - Also in the ../eros/descript/ subdirectory there are sorted excel files that are companions to the above .txt description files. These are subsets of the main spreadsheets. They contain only observations of a specific sub-type. They must be downloaded for use. No html versions exist. A complete guide can be found in the ../eros/descript/observation_key.txt file (linked from front page). Predict Plots - Predict plots (plot of image fields-of-view onto a 3D model of Eros) exist for most observations. These are linked from the spreadsheet in Predict columns. See the ../eros/eros_columns.txt file for an explanation of these plots. Plate maps of low orbit mapping coverage are available for each week that we spent in low orbit and performed 'XREQ' observations. These show total coverage for that week. They are located both in each week's subdirectory, and also in the ../eros/loworbit/ subdirectory. A list of these files can be found in ../eros/loworbit/loworbit_maps.txt. This is linked from front page. A limited number of plots exist for individual XREQ observations. These are linked from the spreadsheets and listed in ../eros/loworbit/loworbit_maps.txt. Trajectory Plots - Sets of trajectory plots for each orbital period during the Eros orbital phase are available. For each period there are two plots: 1) Range to center vs. time, 2) Sub-s/c latitude vs. time. For the two low altitude flyovers there is also a range to surface plot. These are located in the ../eros/traj/ subdirectory, and described in the ../trajectory_plots.txt file. Orbital Info - Text file overview of Eros orbital trajectory information, linked from main page Information regarding EROS ORBITAL MISSION: - Chapter 11 of this document is an overview of the orbital imaging mission - Chapters 12 through 25 give more details for each different orbital period - /eros/descript/observation_key.txt This file is an overview of the sorted spreadsheets and description files available in the /eros/descript/ subdirectory. 1.1 Document Outline 1.0 Introduction 2.0 Cruise Calibrations 1 1996-051 to 1996-178 3.0 Mathilde 1997-015 to 1997-178 4.0 Cruise Calibrations 2 1997-218 to 1997-342 5.0 Earth-Moon Swingby 1998-023 to 1998-026 6.0 Cruise Calibrations 3 1998-210 to 1998-353 7.0 Eros Flyover 1998-357 8.0 Cruise Calibrations 4 1998-363 to 1999-353 9.0 Final Approach to Eros 2000-11 to 2000-45 10.0 Low Phase Flyover 2000-045 11.0 Orbital Mission Overview 12.0 Post-Orbit Insertion 2000-045 to 2000-063 13.0 200 km Orbit - North 2000-63 to 2000-102 14.0 100 km Orbit - North 2000-093 to 2000-121 15.0 50km A Orbit 2000-113 to 2000-189 16.0 35 km A Orbit 2000-189 to 2000-213 17.0 50km B Orbit 2000-206 to 2000-249 18.0 100km Orbit - South 2000-239 to 2000-294 19.0 50km C 2000-287 to 2000-299 20.0 Low Altitude Flyover I 2000-300 21.0 200km Orbit - South 2000-300 to 2000-348 22.0 35km B Orbit 2000-342 to 2001-024 23.0 Low Altitude Flyover II 2001-024 to 20001-028 24.0 35 km C 2001-28 to 2001-43 25.0 Landing 2001-43 ******************************2********************************************* 2.0 Cruise Calibrations 1 1996-051 to 1996-178 **************************************************************************** 2.1 Historical Background This section covers the time period from launch up to just before the Mathilde encounter. Various calibrations with the MSI were performed including software validations, pointing checkouts and calibrations of the camera's radiometric response. 2.2 Sequence Design Each observation is listed here with brief description and references to associated files. Moon1_SW_Validation (1996-051) - First activity following launch. This is a set of calibration images of the moon. Cover had not been deployed yet. The objective was to take a set of images that would serve as a calibration baseline for cover-on imaging. See file /pre_eros/cruisecals_1/launchmoonseq.txt (Contains STOL, but no descriptive summary) Hyakutake_DrkCurr_a (1996-084) Hyakutake_Pointing (1996-084) - See /pre_eros/cruisecals_1/hyakutakeseq.txt (description but no STOL) Hyakutake_DrkCurr_b (1996-084) The opportunity arose to image comet Hyakutake with MSI. It was primarily used as a means for exercising the imaging and pointing capabilities. We did learn that the pointing capabilities on NEAR are excellent, and we also acquired some good images of comet Hyakutake from space. Canopus1 (1996-120) - see /pre_eros/cruisecals_1/canopus1seq.txt (summary and STOL) Canopus2 (1996-123) - see /pre_eros/cruisecals_1/canopus2seq.txt (summary and STOL) The above calibrations were intended to provide info about the camera's radiometric response before and after the cover deploy. Praesepe_GeomCal (1996-123) - see /pre_eros/cruisecals_1/canopus2seq.txt (summary and STOL) LowSunTests (1996-178) - see /pre_eros/cruisecals_1/lowsuntestseq.txt (summary and STOL) These calibrations were intended to provide geometric and scattered light calibrations of the camera. ***************************************3************************************ 3.0 Mathilde - 1997-015 to 1997-178 **************************************************************************** 3.1 Historical Background The Mathilde flyby was first flyby of a carbonaceous asteroid. A major constraint on aimpoint selection had to do with keeping sun on the solar panels throughout the flyby. The only trajectory which would allow us to keep the camera pointed to Mathilde throughout most of the flyby while not violating solar panel constraints was to fly due North over Mathilde (ecliptic north). The miss distance of 1200km was selected because that was the closest we could fly and still be able to turn the spacecraft fast enough to track Mathilde at closest approach. It wasn't so much a problem of maximum rate, but the acceleration needed to change the rate during the few minutes surrounding closest approach. The two primary science experiments of the Mathilde flyby were imaging and gravity. The spectrometers would not be able to do anything useful because of the distance and speed of flyby. The magnetometer remained on, but the other instruments were turned off to conserve power and thus allow the s/c to turn farther off the sun, extending the duration of the flyby imaging. The Mathilde flyby was similar to the Gaspra and Ida flybys in that there was no on-board closed loop tracking available on NEAR. The general problem to be solved was that the ground-based uncertainties in the location of Mathilde at closest approach represented a region of sky that is huge compared to a single MSI field-of-view. The time it would take to cover that region of sky even once with a mosaic of images was larger that the time available for the entire encounter. The odds of capturing the asteroid in the image taken exactly at closest approach in that mosaic were extremely low. To circumvent this problem we had to refine knowledge of Mathilde's location from pictures taken during last day before closest approach, and then have a mechanism for incorporating that knowledge into an on-board sequence pointing update just hours before the encounter. Opnavs were planned to be acquired at intervals of 6 hours beginning at E-42. The last set would be taken at -11 hours. The predicted uncertainty in location of Mathilde relative to spacecraft associated with these images is much smaller than the ground-based uncertainty. Plans for an optional spacecraft trajectory correction maneuver at E-24 hours were also made, although Mathilde would need to be detected in the opnavs at -36 hours in order for there to be enough time to prepare and execute a trajectory correction maneuver based on the analysis of those opnavs. It was uncertain whether Mathilde would be detected at or prior to -36 hours. The main observation sequences were designed to cover a region of sky that represented the 2-sigma uncertainties associated with the opnavs taken at encounter -18 hours. The shape of the uncertainty region was a prolate triaxial ellipsoid, with dimensions 84 x 79 x 230 km. Long dimension was parallel to the downtrack motion of spacecraft (most difficult to determine distance from a point source along line of sight). Cross-track uncertainties, normal to the down-track, were smaller (it is easier to determine location side-to-side by comparing location of Mathilde to stars in the background). There was a 90% chance that the center of Mathilde would lie within the perimeter of this ellipsoidal region, with the most probable location at the center. The basic plan was to try to cover this uncertainty region as many times as possible during the flyby, in an intelligent manner. After many months of evaluating the problem including the various spacecraft, operational, and geometrical constraints, we decided that the best way to get the most efficient repeated coverage was to just start at one end and continue to slew back and forth along the ellipsoid parallel to the long dimension, from one end to the other. Each pass along the ellipsoid would return on full view (or partial view) of Mathilde depending on whether the field of view was wide enough to cover the cross track dimension. It was not possible to do much cross-track slewing because of limited acceleration available on the spacecraft (and also limitations due to smear requirements). However, the only time the field of view was narrower than the crosstrack dimension was during the closest approach slew and the two following slews. For those three observations, we could not guarantee return of full disk of Mathilde. But we could guarantee partial coverage (at least a sliver, even if Mathilde were sitting at the perimeter of the 2-sigma ellipsoid). The slew rates up and down the ellipsoid were largely constrained by smear considerations, except right at closest approach when the spacecraft acceleration was an issue. The rates were designed to limit smear to <1 pixel for the nominal exposure values. We cycled the exposures through three different values to give 500, 1000, and 2000 DN for nominal albedo of Mathilde. There was considerable uncertainty in the estimated albedo of Mathilde. This range of exposure values would guarantee return of at least one good image out of the three covering the possibility of being off in albedo by a factor of up to 8 either way. For instance, if the albedo was a factor of eight brighter than the nominal predict, the exposure calculated to give 500 DN for nominal albedo would actually return about 4000 DN (close to the limit of saturation in this case). When the sequence was uplinked to spacecraft, these mosaics were targeted to the best known location of Mathilde at time of uplink. Uncertainty in it's location at time of uplink was basically the ground-based knowledge uncertainties quoted above. These were huge, much much bigger than the tiny mosaics centered in that region. The Mathilde sequence DEPENDED on the successful acquisition of the images taken at -18 hours AND on a successful trajectory correction at -24 hours, if one was needed. Following acquisition of the images, a new solution for location of Mathilde would be determined, and then a pointing tweak sent to spacecraft. The pointing tweak had two parts. First we would upload a revised spacecraft ephemeris. NEAR carried on-board representations of the planetary and spacecraft ephemerides and these are what drove pointing commands. The revised spacecraft ephemeris would correct for cross-track and downtrack errors in location of Mathilde. I think they kept the old Mathilde ephemeris up there, but represented any new information about location of Mathilde and/or spacecaft as a shift in the s/c trajectory only. Only a revised spacecraft trajectory would be uploaded. Since the sequence pointing was accomplished with target-relative commands, by simply uploading a revised trajectory to the spacecraft, the mosaics would automatically be centered on the new most probable location of Mathilde as known at -18 hours. The second part of the tweak was a timing update. This would correct for any error in downtrack location of Mathilde (or time of arrival at closest approach). It was decided (for a host of reasons) to simply turn the on-board clock forward or backward to correct for any improvement in knowledge of time of flight. We would also take opnavs at -11 hours, but we were not depending on them. If analysis were complete in time, preparations in the ops timeline had been made for a second tweak based on the analysis of those -11 hour opnavs. This would have the effect of better centering Mathilde within the image mosaics. As mentioned above, the nominal sequence was dependent upon the successful execution of the tcm at -24 hours, if needed, AND a successful pointing update. If either were not successful, there was little chance that the the high and moderate resolution sequences would return any pictures of Mathilde. Therefore, as a contingency, we added an observation following the prime encounter imaging which covered a region of sky equivalent to the size of the uncertainties in Mathilde's location if NO opnavs were acquired (the ground-based trajectory uncertainties). This was included in the nominal Mathilde sequence rather than having a second separate sequence on-board, to avoid the possibility of accidentally enabling the wrong sequence. Here's what happened. Mathilde was detected in the - 36 opnav set and it was determined that the TCM was not needed. However, the pointing tweaks were needed. We successfully performed an on-board orbit update and clock shift following the -18 hour opnavs, AND following the -11 hour opnavs. The combined effect of those updates included a 9 second clock shift, and an orbit correction of about 100km. An image of Mathilde was returned in all observations, including an image taken exactly at closest approach. The exceptional skills of the JPL navigation and APL operations teams were confirmed! 3.2 Sequence Design Shamtilly Tests - Five in-flight (on the spacecraft) simulations were performed prior to execution of the actual Mathilde flyby. Main purposes of these tests: perform calibrations, provide operational practice for Mathilde encounter, verify slewing performance of the spacecraft (we put fake trajectories on-board which allowed a realistic rehearsal of actual encounter sequence slewing). Based on this, we tweaked the slewing in the final sequence, solved some problems, retested sequence, etc. Some text descriptions are available in the sequence directory: (1997-015) Sham2CanopusEnctrSeq.txt Darks, Canopus Cal, Encounter slewing test (1997-015) Sham2GeomEnctrSeq.txt Geometric Cal, Encounter slewing test (1997-115) Sham3Seq.txt This was a full-up encounter simulation (1997-141) Sham4Seq.txt This was a full-up encounter simulation (1997-150) Sham5Seq.txt This was a full-up encounter simulation Opnavs- (1997-176 to 179) Point to mathilde, begin slow scan and take Seq 1 twice. Seq 1 was 8 images spaced 2sec apart, 999 ms man exp, filter 0. Therefore, each opnav acquired 16 images while slewing slowly to smear stars and Mathilde across the diagonal of a 2x2 pixel area. Opnav1 E- 42 Hrs Opnav2 E- 36 Hrs Opnav3 E- 30 Hrs Opnav4 E- 24 Hrs Opnav5 E- 18 Hrs Opnav6 E- 11 Hrs ENCOUNTER SEQUENCE (1997-178): *********>>>> An imagelist exists for the encounter sequence. See mathildeimagelist.txt in /pre_eros/mathilde/ subdirectory. *********>>>> Plot files are also available, linked from spreadsheet. The large triaxial ellipsoid shown is the error uncertainty region. It represents the uncertainty in location of Mathilde that would be associated with analysis of opnavs taken at closest approach -18 hours. This region is the 2 sigma ellipsoid. This means, there was 90% chance that Mathilde's center would lie at the perimeter of or within that volume of space. In the second set of plots, Mathilde is shown located at the most probable position (center of uncertainty ellipsoid). Actual location following the pointing updates was not far from that shown. MathildeHighPhase - Eight 3-exposure sets through filter 0 (clear) spaced 18 seconds apart. The three exposures were designed to give 500, 1000, 2000 DN for nominal albedo. This was a single scan across the ellipsoid starting on the far end of the ellipsoid, and ending on the near end. There is a lot of overlap between adjacent 3-exposure sets. At this point the ellipse was fat and collapsed as we were still looking more or less parallel to trajectory. Eros was captured in many of these images (all at high phase). MathildeHiRes1 - One image every 2 seconds through filter 0 (clear) for duration of observation. Three manual exposures per time-step, to cover uncertainty in albedo of Mathilde. There are 30 3-exposure sets in this strip. This strip was the one chance to capture Mathilde at the highest resolution possible. Notice that this strip does not cover full width of the ellipse in cross-track (normal to down-track direction). However, it did give a 90% probability of capturing at least a portion of Mathilde. We started on the near end (close to where the high phase slew terminated), and scanned along the ellipse to the far end. It was necessary to slew in this direction because it gave some small amount of relief to the overall tracking slew through closest approach. This superimposed HiRes 1 slew subtracted from the tracking slew. The timing of this observation was such that we would be pointed right at the center of the ellipse (most-probable location of Mathilde) exactly at closest approach. Turns out, Bill Owen's analysis of the opnavs was spectacular. The orbit determination solutions were nearly perfect. We got a >95% complete global image exactly at closest approach. Mathilde is contained in several overlapping images near closest approach in this series of images. The diameter of Mathilde is almost exactly the width of the fov in these images at closest approach. MathildeHiRes2 - One image every 2 seconds through filter 0 (clear) for duration of scan. Three manual exposures per time-step. There are 18 3-exposure sets in this strip. During this we perform another single swath along the downtrack dimension of the uncertainty ellipse. Since the field of view width was not yet as wide as cross track dimension of the ellipse, we veered to the side a bit to cover one edge of the ellipse. This strip did return a complete view of mathilde from this observation. MathildeGlobal1 - One image every 2 seconds through filter 0 (clear) for duration of scan. Three manual exposures per time-step. There are 10 3-exposure sets in this strip. This was another single swath along the downtrack dimension but this time we veered to the other side of the ellipse (fov still not quite covering the cross track width of ellipse. HighRes 2 and Global1 individually offered less than 90% chance of capture. But together they gave the full 2 sigma probability of capturing all of Mathilde. MathildeGlobal2 - One image every 2 seconds through filter 0 (clear) for duration of observation. Three manual exposures per time-step. There are 9 3-exposure sets in this strip. Actually, the last image of the last set is part of the first 5-filter set in multispectral I. This is another single swath along downtrack dimension. Veer to the same side as in HighRes2. Multispectral 1 - Still taking images once every 2 seconds but for this strip we take 15 6-filter sets. (filters 0,1,2,3,4,5; all manual exposure). See imagelist; exposure values are cycled through three sets as before. This represents another pass across the uncertainty ellipse, but the fov is quite large now relative to the ellipse and covers more than 2-sigma crosstrack dimension. The first 13 5-filter sets were taken while slewing down the length ellipse, the last two were taken while returning to nadir. Multispectral 2 - Here we take several 7-filter sets, some of which have multiple exposures per filter. Images still being taken once every 2 seconds. Slewing is that we return to the nadir position and hold there. No-Opnav - Still taking images every 2 seconds. Now we take 20 4-exposure sets through clear filter. Three of the exposures are 1/2 nominal, nominal and 2x nominal exposed for Eros. The fourth is a 999ms exposure for small objects. Six of the 20 4-exposure sets are taken during the first slew, and 14 are taken during the second slew (see below for slew description). Before imaging began we repositioned to one end of the 'no-opnav' uncertainty ellipse. This is a large region of sky that represents uncertainty in Mathilde's location if we did not acquire any Opnavs. We slewed across the region once (first slew) to the other side, and then back to the starting position (second slew). Satellite Search - Still taking images once every 2 seconds, we took several 7 filter sets and a long series of clear-filter images which was basically centered on nominal location of Mathilde. We slewed to a second position slightly overlapping the previous position in the -y direction. *****************************4************************************* 4.0 Cruise Calibrations 2 - 1997-218 to 1997-342 ******************************************************************* 4.1 Historical Background Sorry, couldn't find the sequences for these observations. No descriptions available. More radiometric calibration of MSI. These are similar to previous canopus calibrations preformed in cruisecals_1 section. 4.2 Sequence Design SWUploadValidation1 - 1997_101 Canopus3 - 1997-218 Canopus4 - 1997-286 Canopus5 - 1997-342 *****************************5********************************************** 5.0 Earth-Moon Swingby 1998-023 to 1998-026 **************************************************************************** 5.1 Historical Background The main purpose for the Earth Swingby was to perform a gravity assist with the Earth. The project allowed the instrument teams to perform calibrations with the Earth and Moon during the flyby. A quick overview of the observations performed with MSI and NIS follows. 5.2 Sequence Design The spacecraft flew over the North Pole of the Earth and down across Asia, flying generally over Iran, Iraq, the Persian Gulf, Saudi Arabia, and Africa, and receding from the Earth in such a manner that allowed viewing of the South Pole and Antarctica. Earth 1 - Observations taken of Asia and Middle East. No slewing. Pointing fixed by spacecraft solar panel constraints. Took pictures and spectra as boresight ground track passed over these regions. Earth 2 - a. Following the Asia imaging was an Africa observation which was basically consisted of a slew that took boresight north-south along southern Africa. NIS performed mirror scans while MSI took 7-filter sets at 4 different positions along the scan. b. After this was another MSI/NIS calibration pointed at Antarctica. c. Then we performed a 1.5 day Earth spin movie, targeting to the South pole of the Earth. This includes 7 scattered light cal sequences (the last taken 3 days after flyby). Moon 1 - Set of calibrations with MSI and NIS. This interrupts the Earth spin movie for about 4 hours at 23/1900. Moon 2 - MSI/NIS Coalignment test. Follows the Earth spin movie. ********* IMPORTANT NOTE ABOUT EARTH/MOON FLYBY ****************** The following files are available in /sequence/pre_eros/earthmoon_flyby/ Detailed descriptive summaries of both MSI and NIS observations are linked from the spreadsheet and available in: /pre_eros/earthmoon_flyby/earth1.txt /pre_eros/earthmoon_flyby/earth2.txt /pre_eros/earthmoon_flyby/moon1.txt /pre_eros/earthmoon_flyby/moon2.txt The actual Earth and Moon sequences in STOL: /pre_eros/earthmoon_flyby/earth1seq.txt /pre_eros/earthmoon_flyby/earth2seq.txt /pre_eros/earthmoon_flyby/moon1seq.txt /pre_eros/earthmoon_flyby/moon2seq.txt A special imagelist just for the EarthMoon swingby (note, the excel spreadsheet is easier to use): /pre_eros/earthmoon_flyby/earthmoonimagelist.txt /pre_eros/earthmoon_flyby/earthmoonimagelist.xls PLOTS - numerous plots are available, linked from the Predict columns. ******NOTE - there is an ERROR in the scatz.gif plot. Where it says +Z (annotating the slew direction of frames away from moon), it should say -Z. See moon1.txt for explanation. *******************************************6********************************* 6.0 Cruise Calibrations 3 - 1998-210 to 1998-353 ***************************************************************************** 6.1 Historical Background Following the Earth Moon Swingby things were quiet for about 6 months on the spacecraft. We were busy with implementation of the SEQGEN software, developing the command macros that we needed for Eros, and expanding the capabilities of the ORBIT software for the orbital phase. The need for a single repeat capability in the MSI DPU became apparent, as well as discovery of some problems with autoexposure. The MSI DPU software was fixed and uploaded to the spacecraft. The first imaging activity following earth flyby was a test of these software fixes. This was followed by a guidance and control test. After that we began the nominal approach imaging that would lead to orbit insertion on January 10, 1999. These tests and approach imaging observations are described below. 6.2 Sequence Design Since most of the observations and calibrations in this section were unique I have simply listed them all individually, and supplied some descriptive text. SWUploadValidation2 - (98-210) Test of upgrade to MSI DPU software that fixed autoexposure and added the single repeat capability. Single repeat gave us a simple and cheap method of repeatedly executing the same sequence. Point to J2000: -0.061492,+0.603155,-0.79525 Set MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,1,92,0,2000,750,0 Execute Seq 2 (8 filters, manexps 15 92 229 174 478 262 979 999, fast), followed by Seq 3 (8 filters, autoexp, fast) 2 minutes later. Set MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,1,92,10,2000,750,0 Execute Seq 4 ( filters 1 3 5, autoexp, fast) Set MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,1,300,0, 2000,500,750 Execute Seq 6 ( filter 1, autoexp, fast) Set MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,1,92,0,2000, 750,4000 Execute Seq 7 (filter 1, autoexp, fast) Set MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,0,15,0,90, 750,85 Execute Seq 8 (filter 0, autoexp, fast) Execute single repeat of Seq 9 (filter 1, manexp 92ms, fast). Three executions of seq 9, spaced 15 sec. Execute single repeat of Seq 10 (7 images through filter 1, manexp 92ms, and 1 image through filter 0 with manexp 0ms, fast). Two executions of seq 10, spaced 3 sec apart. Deliberately trying to get an error. Set CAS_MSI_AUTO_EXPOSE,12267,2000,803,1057,385,702,188,108,10,1,92,0, 2000,750,75 Execute Seq 11 (7 images through filter 1, manexp 92ms, and 1 image through filter 0 with manexp 0ms, fast) followed 28 seconds later by Seq 12 (8 filter 0 images with manexp 10ms each, fast). Execute the MSI_CANCEL_IMAGE sequence. Execute an MSI_DOUBLE_REPEAT CAS which is to execute Seq 13 (1 filter 6 image, autoexp, fast), followed 2 seconds later by Seq 14 ( one filter 6 image, manexp 0 ms). Then repeat execution of the pair. (this was to test the only way we had at the time of doing monochrome clean observations). SpacecraftRollTest_a and _b - (98-231) Test to check accuracy of star camera attitude information. No summary available for this, but Seq file available in 98229_msi_nis_sasf.txt; see MSI_POINTING_TEST. The last frame in this observation is OPNAV_E Test. Should have been called out separately. OpnavTest - (98-273) Another test of Opnav_E. One clear filter manexp 999ms image. We never actually used this Opnav_E CAS again. MonoLightCurveSeq_1a - (98-309) This observation was the first on-board light curve measurement to evaluate the state of Eros rotation and its shape. The observation executed Seq 26 (1 clear filter image, fast,autoexp) every 5 deg of rotation for 1.2 spin periods. This was followed by 2 executions of Seq 30 (1 image, clear filter, manexp 999ms, no compr). MonoLightCurveSeq_1b - (98-313) This observation was a practice for the multispectral lightcurve that was planned to be taken just before orbit insertion. It served as a test for some complicated sequencing, but the primary objective was to test the data flow through the SDC. We did not have downlink available to perform the full multispectral rotation sequence. This one only goes for 1/3 of Eros rotation. Seq 25 (8 filters, no compression, autoexp) is executed every 30 deg for 4 executions; in between the above we alternate between seq 20 (3 filters,fast,autoexp) and seq 24 (4 filters, fast, autoexp), every 79 seconds (equiv to 1.5 deg of Eros rotation). Three filter sequence is 1,3,4. Four filter sequence is 1,2,3,4. MonoLightCurveSeq_2 - (98-323) This was the second real light curve measurement. Same as the first, 1 clear filter image every 5 deg of rotation for about 1.3 rotations. Note: The following opnavs are also described in /eros/descript/opnav.txt, and also in the sequserguide.pdf ---- Opnav A1-7 - (98-324) These opnav sequences were designed to be used while Eros was subpixel. Take 16 images of Eros through clear filter while slewing slowly to smear Eros across a 2x2 pixel diagonal. Opnav B1 - (98-324) Only executed once. Opnav B's were supposed to be used when Eros became resolved (larger than a pixel). But we decided to start them up early and interleave them with the Opnav A's. Opnav B takes 8 images of Eros (5 autoexposures for Eros, 3 man exp 999ms, all through clear). We only used this Opnav once. See description of Opnav BP below. Opnav C1 - (98-324) This was a test of the spacecraft body fixed scanning coordinate system and did not use the real Opnav_C CAS. However, it was the same mosaic type, which was a 1x1 (single position) followed by a 2x2 mosaic, 1 clear filter, fast, autoexp at each position. Opnav BP 3,5,6,7 - (98-348) Opnav_BP was executed several times as a part of the approach sequence. We were concerned about the design of Opnav B, that the Eros pictures were entirely dependent upon autoexposure working correctly. Acquisition of useful opnavs was critical to the mission success. Therefore, Opnav BP was created, in which 2 of the 5 autoexposures were converted to short manual exposures (4, 60ms) as back up in case we had problems with autoexposure algorithm. MonoLightCurveSeq_3 - (98-349) Third approach light curve sequence. This time, 1 clear filter image was taken centered on Eros about every 8.7 deg of Eros rotation for 1.3 rotations. *******************************7********************************************* 7.0 Eros Flyover - 1998-357 ***************************************************************************** 7.1 Historical Background The original mission plan for Eros orbit insertion called for a series of 4 rendevous burns beginning on Dec 20, 1998 and concluding on Jan 10, 1999 when the spacecraft would enter Eros orbit. This plan was altered when on Dec 20, 1998, Rendezvous burn 1 aborted after 1 second. The project lost contact with the spacecraft for over a day, but an intermittent signal was eventually picked up. After hasty analysis contact was reestablished. Since the burn had not executed, the spacecraft was still moving at a large velocity relative to Eros. It would fly past Eros on Dec 23, midday EDT. Project allowed a flyby imaging sequence to be built and sent to the spacecraft as this might be the only chance we would have to image Eros. Imaging design for the flyby was dependent on knowing the uncertainty in location of Eros relative to the spacecraft. Just as in the Mathilde flyby, each time you cover this region of sky with images, you hopefully capture one view of Eros somewhere within that mosaic. Unfortunately, the size of the uncertainty region for this flyby was uncertain! Navigation only had a little bit of doppler following the aborted burn to work with. The spacecraft had been tumbling, and its trajectory was uncertain. Nevertheless, using their best estimate of the uncertainty region, together with analysis with our visualization software, we determined that a 2x2 mosaic would likely cover this region through the flyby. Turns out this was a little less conservative than should have been because Eros was actually sitting outside that region. Despite that, serendipity and geometry allowed the first half of the imaging (through closest approach) to capture Eros within the mosaics. Some time after closest approach we lost Eros in the 2x2 target region. The images returned from this flyby allowed development of a 5 degree shape model of Eros to be constructed for the portions of Eros illuminated during the flyby. Prior to the flyby we only had the triaxial ellipsoid determined from ground-based lightcurves. Solar illumination on Eros during the flyby was southerly (sub solar latitude was -32 deg), hence, much of the north side of Eros was not visible at the time of the flyby. The model interpolated over those areas and the result was a volumne estimate that turned out to be good to about 15%. We also got a good calibration on the spin phasing of Eros. This was a trememdous help for planning of the orbital mission that would begin in Feb, 2000. 7.1 Sequence Design Eros Flyby Sequences performed on 1998/357 includes the following three parts. NIS data was taken simultaneously with the MSI sequences. SatSrch1_contingency - A pre-flyby satellite search consisting of a 4x4 mosaic through the clear filter. At each position in the 4x4, four manual exp images were taken (4, 999, 999, 4 ms), fast compression. Pointing: mosaic centered on Eros' most-probable location. MultispecRot_contingency - This was a set of observations that went on for over 5.5 hours, more than one full spin period of Eros, and was intended to repeatedly image Eros plus trajectory uncertainty region. This main sequence began with 11 1/2 executions of the following pair of observations: 1) 7 filters with fov centered on Eros most-probable location (1x1), 2) 7-filters at each position in a 2x2 mosaic centered on Eros' most-probable location. The pair was repeated every 13 minutes. After 11 executions of the pair, plus one additional 1x1, we scheduled a 4x4 mosaic through the clear filter. The sequence was timed to occur at the predicted closest approach time as a backup in case we had been too conservative with the uncertainty ellipse size. In other words, in case the 2x2's were not large enough, hopefully we would at least capture an image of Eros at closest approach in this 4x4. Following the 4x4 mosaic, we resumed with the execution of the 1x1 plus 2x2 7 filter sequence pairs as above. Fourteen more pairs were executed. SatSrch2_contingency - Immediately following the above, a post-flyby satellite search was performed, similar to the pre-flyby sat search. This consisted of a 4x4 mosaic through the clear filter. As above, 4 clear filter manual exposures were taken for at each of the 16 positions (4, 999, 999, 4 ms). (no plot available for this one, but the mosaic looks exactly like satsrch1_contingency.gif) *********IMPORTANT NOTE about files available for Eros Flyby! ******* An imagelist, and plots are available for the above activities. They are located in /eros/98357/erosflyby_imagelist.txt /eros/98357/mosaicname.gif ..... The gif plot names correspond to the mosaic names as noted in the imagelist. Plots exist for all of the 1x1s, about 1/3 of the 2x2s, satsrch1, and the 4x4 at closest approach. Please note that as these were PREDICT plots, they display Eros at its most likely location as we believed it to be prior to the flyby. We targeted the mosaics to be centered on that most probable location of Eros. Eros' actual location was not at this point. Therefore, in the actual images, Eros will at a different position than where these plots indicate. The rotational state of Eros should be pretty good. Mosaic shape and frame-to-frame overlap should also be good. ************ADDITIONAL NOTES!!******* 1) Satsrch2 looks identical to satsrch1. I did not have a satsrch2 plot so I i linked the satsrch1 plot to Satsrch2 observation. 2) There are multiple plots for Multispecrot_contingency. Only the first plot is linked from the predict column. You must go to directory eros/98357/ to access the others. ********************************8******************************************** 8.0 Cruise Calibrations 4 - 1998-363 to 1999-353 ***************************************************************************** 8.1 Historical Background About a week after the burn abort, the project was able to reschedule and successfully execute the large burn with the main engine that eliminated most of the Eros-relative velocity. This put the spacecraft on course for a second chance at an orbital mission 1 year later. The spacecraft would stay within about 1 million miles of Eros for the duration of that period (it was visible with the camera as a point source) as it chased Eros around the sun. Gradually the distance between s/c and Eros would decrease and the second attempt at orbit insertion would occur on Feb 14, 2000. An unfortunate consequence of the anomaly was that during the burn abort recovery period, the spacecraft released a large percentage of the on-board fuel. Some of the by-products ended up depositing onto the camera lense and created serious scattered light problems in many of the filters. For most of this year following the Eros flyby, the science teams were allowed only a few calibrations. MSI used these calibrations to attempt to characterize the scattered light problem. In addition to the calibrations, a number of opnavs and lightcurves were performed to track the position of Eros and monitor the spin phasing of Eros. 8.2 Sequence Design Once again, for this section the individual observations are listed with descriptive text. For a description of the Opnav sequences in this section, see notes in above section 6, opnav.txt, and the sequserguide.pdf. These opnavs were performed as a part of the post burn anomaly recovery efforts. Opnav_A N1-N5 (98-363 to 99-007) Opnav_C N1-N5 (98-363 to 99-007) Opnav_BPrime N1-N5 (98-363 to 99-007) Opnav_CA_1 - 9 (99-19 to 99-42) (these were simply a concatenation of Opnav_A and Opnav_C as described separately) MonoLightCurveSeq_4 - (99-45) During the year of cruise between Eros flyby and Eros orbit insertion we attempted to monitor the state of Eros with observations such as these. The data were used to check the shape model, the rotation rate, spin phase (sub-s/c long), hints of albedo variation. Reference: Clark, et al, "NEAR Lightcurves of Asteroid 433 Eros", Icarus 145, p641-644 (2000). This particular light curve consisted of taking 1 clear filter image every 7.1 deg of rotation for 1.1 Eros rotations. Manual exposure, 999ms, fast. StarClusterCal_1 (99-103) - First position centered on J2000 (0.1548263,0.4880745,-0.8589599), followed by a 2x2 centered on same position. One clear filter image, manexp 999ms, fast, at each position. CanopusCal_1a (99-103) - See /eros/descript/canopuscals.txt MonoLightCurveSeq_5 (99-104) - One clear filter image every 5 deg of rotation for 1.1 Eros rot. Man exp 999ms. CanopusCal_1b (99-105) - See /eros/descript/canopuscals.txt StarClusterCal_2 (99-132) - First position centered on J2000 (0.1548263,0.4880745,-0.8589599), followed by a 2x2 centered on same position. One clear filter image, manexp 999ms, fast, at each position. CanopusCal_1c (99-133) - See /eros/descript/canopuscals.txt CanopusCal_2a - (99-154) See /eros/descript/canopuscals.txt StarClusterCal_3 - (99-166) First position centered on J2000 (0.1548263,0.4880745,-0.8589599), followed by a 2x2 centered on same position. One clear filter image, manexp 999ms, fast, at each position. CanopusCal_2b - (99-166) See /eros/descript/canopuscals.txt MultispectralLtCrve_C1 - (99-166) Cruise light curve to monitor shape and rotational state of Eros. One set of three manual exposure 999ms images (filters 0, 1, and 5) every 7.3 degrees of Eros rotation for 1.1 rotations. SWUploadValidation_3 - (99-181) This test sequence exercised many functions of the msi software following upload of a new flight s/w. The software changed compression Table 7 so that it would compress a throwaway image to practically nothing. Background: During the rendezvous burn anomaly, material was deposited on the camera lense which created a very serious scattered light problem for MSI through all of the filters. To mitigate this problem, Scott Murchie devised a method of taking images which involves taking a zero exposure in addition to the normal autoexposure. The information returned in the zero exposure was used to subtract out scattered light from the normal exposure image. An observation performed in such a manner is called a 'clean' observation. For observations which use multiple filters, it was necessary to take a zero exposure frame for each different filter for which there was a regular exposure. Operationally, the only way to do this was to first take all of the normal exposures (usually, but not always autoexposure) through the various filters together as a set. After this we would take all of the zero exposures (manual) through the same set of filters. After that, however, at the end of the zero exposure set, we had to add ADDITIONAL zero exposure frame for the sole purpose of making sure that the filter wheel was in motion during the readout of the final filter of the zero exposure set. Without that additional frame the filter wheel would have been in motion for all of the other normal and zero exposures in the set, except that last filter. Calibration of that final zero exposure image would have been invalid if the filter wheel were not moving. The additional frame was of no use other than for the purpose of making the filter wheel move. We didn't need to play it back, but there was no way to not record it with the rest of the observation. Enter the new Table 7. The new table 7 was a way of compressing that 'throwaway' image to practically nothing so we did not waste downlink time on an image that was not needed. No verbal description of this calibration. But if you want to know what happened, see /eros/99179/99179_final_sasf.txt and find the request called MSI_UploadTst. It's pretty easy to decode. (not much slewing, just a bunch of imaging) CanopusCal_3a - (99-197) See /eros/descript/canopuscals.txt CanopusCal_3b - (99-197) See /eros/descript/canopuscals.txt StarClusterCal_4 - (99-197) First position centered on J2000 (0.1548263,0.4880745,-0.8589599), followed by a 2x2 centered on same position. One clear filter image, manexp 999ms, fast, at each position. MultispectralLtCrve_C2 - (99-197) Cruise light curve to monitor rotational and photometric states and shape of Eros. One set of three manual exposure 999ms images (filters 0, 1, and 5) every 7.3 degrees of Eros rotation for 1.1 rotations. Opnav_D through K_Tests - (99-353) These were tests of the main Opnav CASs we intended to use for orbital ops. Purpose was to make sure the slewing patterns and corresponding imaging would execute properly. Basically these opnavs take one clear filter, autoexposure, fast compressed image at each position in some mosaic pattern. The letter of the opnav determines the shape of the mosaic (see /eros/descript/opnav.txt). Pointing was to a star field. ********************************9******************************************** Chapter 9 - Final Approach to Eros (2000-11 to 2000-45) ***************************************************************************** 9.1 Historical Background Final approach to Eros occurred at a time when solar illumination on the asteroid was high on the north side (sub solar latitude +78 deg). The relative approach velocity was small and hence the range to Eros, which was only 48000 km on Jan 11, decreased slowly over this last month leading up to orbit insertion. During time period, Eros grew in size from about 7 short pixels on Jan 11, to about 100 pixels on Feb 10, 4 days before orbit insertion. In last images taken before orbit insertion, Eros was about 380 pixels across, and still fit within a single MSI field-of-view (fov). On approach to Eros we performed many observations that prepared us for entry into orbit. Most important were the optical nav sequences which included daily monitoring (Opnav_BPs), rotation movies, and the satellite searches. Mosaicking was not necessary because Eros plus navigation uncertainties fit within one field-of-view the entire time. NIS performed several important calibrations which are also described here. 9.2 Sequence Design Approach Opnavs: --------------- OPNAVBP's - Starting on January 14, 2000 we took an Opnav_BP sequence about 3 times each day. See opnav.txt. OPNAVBP100 through 140 (2000-14 through 2000-42) Special Note about Opnav_BPs: On tuesday Feb 1, Bill Owen reported that he was not able to see stars in the OpnavBPs because of scattered light through the clear filter (autoexp). He and Scott decided to change the sequence defs for OpnavBPs to make seq 29 be one manexp 150ms through filter 4, seq 9 to be four man exp 999 through filter 4, and seq 8 to be 3 autoexp through filter 4. Karl sent a real-time command Tues afternoon to make this change. Plans were made to modify seq 00038 to make the same changes to seq def file and also to modify the autoexposure setup for Opnav BPs. But this didn't happen right away. Next morning we found out that the s/c had gone into safing (see /eros/00031/NOTES.00031 regarding a problem that occurred with burn abort). We incorporated these changes to the opnav imaging into the 00033 and 00035 loads with one change from the real time command sent Tuesday. The change is that in 00033, and 00035 we went back to using clear filter for the manual 999 exp. Summary of opnav_bp changes: sequences sequence pre-00031 rtc 00031 rtc 00033 and after seq 29 1 man clr 999ms 1 man filt4 150ms 1 man filt4 150ms seq 8 3 auto clr 3 auto filt4 3 auto filt4 seq 9 4 man clr 4 man filt4 999ms 4 man clr 999ms (4,60,999,999ms) Canopus Calibrations - -------------------- MSI_Cancal4b - (11/0125) See /eros/descript/canopuscals.txt MSI_Cancal4a - (12/0040) - See /eros/descript/canopuscals.txt MSI_Cancal5 - (38/0610) - See /eros/descript/canopuscals.txt Satellite Searches: ------------------ We performed three satellite searches. The first was satellite search A about 1 month before orbit insertion. Sat searches B and D were of different design and were performed closer to orbit insertion. SatSrchA - (2000-13/0415) SatSrchB - (2000-28/0810) SatSrchC - (canceled because of a problem that occurred in 00031, never executed) SatSrchD - (2000-41/0145) Please see /eros/descript/satsearch.txt for details of these designs. Plots available: /eros/00010/msi_satsrcha.gif /eros/00024/msi_satsrchb.gif /eros/00038/msi_satsearchd.gif Approach Rotation Movies (color and monochrome): ----------------------------------------------- Multiple purposes for these movies: 1) Watch Eros grow in size on approach. 2) Navigation needed the monochrome movies for establishing new landmarks at each new resolution, 3) MSI and Navigation also used them to refine shape model, determine spin phase state (this was extremely important for future sequence planning, especially for NIS low phase flyover). The color sequences were included for science (no guarantee that spacecraft wouldn't break at any time). Low resolution color data would be better than nothing. Also used for photometry, exposure determination, checks on autoexposure function. A region representing Eros plus navigation uncertainties was smaller than the size of a single MSI frame for all of these approach movies. Normally we pointed the center of MSI fov (or NIS position 75, which is near the MSI boresight) on Eros nadir and held that position throughout the observation. No slewing. Terminology: - The terms 'MSLtCv' and 'MultispectralRots' stand for multispectral light curves and rotation sequences that take multiple filters every x deg of rotation. - The term 'Movie' generally indicates a monochrome sequence where we take one filter every x deg of rotation (for nav) - The term 'GM' is short for global morph; these are also monochrome (for nav). Same as a Movie in every way. Please see /eros/descript/approachmovies.txt and approachmovies.xls APPROACH ROTATION SEQUENCES doy/hhmm size of 35km obs name description in short pix ------- ----------- ------------- --------------------------------- 353/2115 4 MultispctrlRotSeq - 1 clr filter, table5/fast image every .5 deg of rotation for 1.1 Eros spin period , followed by 8 filters every 10 deg for 5 iterations (50 deg of rotation) 12/0500 8 MSI_Movie 1 - 1 filter 4, table5/fast image every 1/2 deg for 1.1 rotations 13/1215 8 MSI_MSLtCv1 - 8 filters, lossless(fast) every 30 deg for 1 rotation 18/0915 10 MSI_MSLtCv2 - 8 filters, lossless(fast) every 30 deg for 1 rotation 22/0545 12 MSI_Movie3 - 1 filter 4, table5/fast image every 1/2 deg for 1.1 rotations 26/0215 16 MSI_MSLtCv3 - 8 filters, lossless(fast) every 30 deg for 1 rotation 29/0815 21 MSI_MSLtCv4 - 8 filters, lossless(fast) every 30 deg for 1 rotation 35/0635 48 MSI_NAVMovie - 1 filter 4 table5/fast image every 15 deg for 1 rotation 37/0200 57 MSI_Movie6 - 1 filter 4, table5/fast image every 1/2 deg for 1.1 rotations 37/0831 58 MSI_MSLtCv6 - 8 filters, lossless(fast) every 5 deg for 1.1 rotations 40/0825 89 MSI_MSLtCv7 - 8 filters, lossless(fast) every 30 deg for 1.1 rotations 41/0910 112 MSI_Movie7 - 1 filter 4, table5/fast image every 1/2 deg for 1.1 rotations 42/0250 139 MSI_GM_1 - 1 filter 4, table5/fast image every 1/2 deg for 1.1 rotations 42/0830 150 MSI_MSLtCv8 - 8 filters, lossless every 30 deg for 1.1 rotations 43/0045 192-209 MSI_MSRot_1a - 1 filter 4 image every 1/2 deg for 1.1 rotations 43/0623 201-237 MSI_MSRot_1b - 7 filters every 13 deg for 1.1 rotations NIS Calibrations: ---------------- The sequencing of these tests are described in detail in several text files located in /eros/descript directory, as referenced below. Both the NIS and support MSI activities, plus the pointing are described. A few plots for both instruments are also available. Only the observation names for the MSI support imaging are listed in the spreadsheet (because this is an MSI spreadsheet). Please see the NIS browse area to find associated NIS data. 1. NIS Raster Tests - MSI_NixRasTstNarrw - (25/0345) - Support imaging for NIS Narrow Raster Test MSI_NixRasTstWide - (25/0858) - Support imaging for NIS Wide Raster Test The NIS and MSI sequences for these two tests are described in great detail in /eros/descript/rastertests.txt Plots are available for the nis observations, as well as the support msi frames that were taken. nis_nixraststnarrw.gif msi_nixraststnarrw.gif nis_nixraststwide.gif msi_nixrastxtwide.gif 2. NIS Mirror Plane Test MSI_MirrorPlaneSup - (31/1513) The NIS and MSI activities of the NIS Mirror Plane test are described in /eros/descript/mirrorplane.txt plots /eros/00031/nis_mirrorplanenar.gif 3. NIS Mirror Geometry Test MSI_MirrorGeomSup1 - (31/0640) MSI_MirrorGeomSup2 - (36/0110) The Mirror Geom test is described in /eros/descript/mirrorgeom.txt plots available: msi_mirrorgeomsup1a.gif msi_mirrorgeomsup1b.gif msi_mirrorgeomsup2a.gif msi_mirrorgeomsup2b.gif nis_mirrorgeom.gif - generic plot **********************************10***************************************** 10. Low Phase Flyover - 2000-045 ***************************************************************************** Objective was to fly the s/c through zero sun line allowing NIS the opportunity to image northern hemisphere at near zero phase angle (high sun, no shadows). This would return the best data for this instrument from the mission. These turned out to be the most complicated sets of sequences built throughout the mission. The normal instrument boresights could not be pointed to Eros during this event since this would require taking the panels 90 deg off the sun. However, built into the NIS is the capability to slew the mirror to the anti-sun direction (s/c -z direction). The exceptional guidance and control capabilities on-board NEAR allowed for some creative pointing regimes. The observations are described in detail in a section of the sequserguide.pdf. No imaging during this time period (solar panel constraints). Closest approach occurred prior to orbit insertion. SUN . . dots represent . s/c trajectory . . . | . | . |200km . | / . | \ Eros Eros north pole pointing roughly to sun at this time ***********************************11**************************************** 11.0 Orbital Mission Overview ***************************************************************************** 11.1 Historical Background Following the successful entry in to orbit, NEAR remained in orbit about Eros for almost exactly one year. At the time of orbit insertion, the North pole of Eros (which lies roughly in it's own solar orbital plane) was roughly pointing toward the sun, and was perpetually illuminated. Sub-solar latitude was about 58 N, the most northerly it would be during the orbital mission. The south polar region was in perpetual darkness. Eros' solar orbital period is about 1.7 years. As Eros (and the spacecraft) proceeded around the sun during the one year orbital mission, the sub-solar latitude gradually moved to the south, bringing perpetual darkness to the northern hemisphere, and full illumination to the southern pole region by late summer, 2000. This diagram is a generalization. The orbital planes were not always perfectly normal to the direction to the sun. ^ North pole | shadowed ______|_______ /xxxxxxxxxxxxxx \ X - - - - |xxxxxxxxxxxxxxxx | - - - - 0 S/C ORBIT EQUATORIAL, (this side going | | retrograde (this coming into page) \______________ / out of the page) | | V South Pole SPIN of Eros is 'right handed' X S/C ORBIT POLAR wrsp to North pole. | (s/c going (right side going into page, | into page) left side coming out of page) ^ North pole | ___ ______|_______ / \ / xxxxxxxx \ | SUN | | xxxxxxxx | \_ __ / | xxxxxxxx | \________xxxxxx / | | V South Pole | | 0 (s/c coming out of page) ^ North pole | ______|_______ orbit / \ 0 - - - - | | - - - - X S/C ORBIT EQUATORIAL, (s/c coming plane |xxxxxxxxxxxxxxxx | prograde out of page) \xxxxxxxxxxxxxxx/ (s/c going into page) | | V South Pole shadowed In the NEAR spacecraft design, the solar panels are fixed on the spacecraft. The plane of the solar panels is normal to the direction of pointing of the high gain antenna (s/c +Z). All optical instruments are boresighted together, and point in the s/c +X direction, normal to the +Z axis (which is in the plane of the solar panels). Solar panel illumination requirements demanded that the angle between the sun and the normal to the panels (+Z) be less than 30 to 45 deg. The maximum value depended on power, distance from the sun, and other considerations and varied throughout the mission. This constraint drove the mission orbital design. At any time, the spacecraft orbital plane had to be roughly normal to the direction to the sun. This is the only configuration that could allow the solar panels to satisfy illumination constraints while simultaneously allowing the instruments to view Eros. As the spacecraft proceeded in an orbit about Eros, a slow roll roughly about the direction to the sun allowed the instrument boresights to maintain viewing of Eros. Eros solar orbital period is about 1.7 Earth years. As Eros progressed in it's orbit about the sun during the year long orbital mission, the orbital plane gradually shifted to remain approximately normal to direction to sun. Mission planners put us into prograde orbits in the beginning of the mission so to avoid the need for a plane flip during the summer. By the end of the year, after going through the polar orbit period, we ended up in a retrograde orbit. The orbital mission was divided into phases corresponding to the various orbits that were achieved. The table below (constructed with info from David Dunham and Jim McAdams, 6/21/01) shows the 25 orbit correction maneuver times and a description of each orbit. Each time indicates entry into that orbit. 'Inclination' refers to the angle between the s/c orbital plane and equatorial plane of Eros. If the number is positive it means the orbit was prograde with respect to Eros' spin. If the number is negative it means the orbit was retrograde with respect to Eros' spin. Eros Orbital Mission Overview Name year mo/day doy hh:mm:s orbit radii inclination period # of orbits (km) (deg) (days) OIM 2000 2/14 045 15:33:05 321 x 366 35 21.8 .5 Post-Orbit Insertion A OCM-1 2000 2/24 055 17:00:00 365 x 204 34 16.5 .5 Post-Orbit Insertion B OCM-2 2000 3/3 063 18:00:00 206 x 203 37 10.1 2.7 200 km North OCM-3 2000 4/2 093 02:03:20 209 x 100 55 6.7 1.5 Transition 200x100 OCM-4 2000 4/11 102 21:20:00 101 x 99 59 3.5 3.2 100km North OCM-5 2000 4/22 113 17:50:00 101 x 50 64 2.2 4.5 100x50 Transition OCM-6 2000 4/30 121 16:15:00 52 x 49 90 1.2 55.2 50km A OCM-7 2000 7/7 189 18:00:02 51 x 35 90 1 6.6 50 x 35km Transition OCM-8 2000 7/14 196 03:00:02 35 x 39 90 0.8 13.7 35 km A OCM-9 2000 7/24 206 17:00:00 36 x 56 90 1.1 6.7 35 x 50km Transition OCM-10 2000 7/31 213 20:00:00 52 x 49 90 1.2 6.7 50km B OCM-11 2000 8/8 221 23:25:00 52 x 50 -75 1.2 14.1 50km B (continued) OCM-12 2000 8/26 239 23:25:00 49 x 102 -67 2.3 4.4 50 x 100km Transition OCM-13 2000 9/5 249 23:00:02 100 x 103 -65 3.5 10.9 100km South OCM-14 2000 10/13 287 05:45:00 98 x 50 -50 2.2 3.5 100 x 50km Transition OCM-15 2000 10/20 294 21:40:00 52 x 50 -47 1.2 3.2 50km C OCM-16 2000 10/25 299 22:10:00 51 x 19 -47 0.7 1 Low Alt Flyover I OCM-17 2000 10/26 300 17:40:00 64 x 203 -35 5.4 1.4 Transition to 200km OCM-18 2000 11/3 308 03:00:00 196 x 194 -33 9.4 3.5 200km South OCM-19 2000 12/7 342 15:20:00 193 x 34 -1 4.2 1.5 200 x 35km Transition OCM-20 2000 12/13 348 20:15:00 38 x 34 -1 0.8 55.9 35km B OCM-21 2001 1/24 024 16:05:00 35 x 22 -1 0.6 6.1 Low Altitude Flyover IIa OCM-22 2001 1/28 028 01:25:00 37 x 19 -1 0.6 1.3 Low Altitude Flyover IIb OCM-23 2001 1/28 028 18:05:00 36 x 35 -1 0.8 6 35 km C OCM-24 2001 2/2 033 08:51:00 36 x 36 -1 0.8 5.5 (35km, tweak for landing) OCM-25 2001 2/6 037 17:43:56 36 x 36 -1 0.8 5.4 (35km, tweak for landing) EMM-1 2001 2/12 043 19:46:02 down to 6 -1 to 36 0.8-0.3 7.8 Descent to surface (time s/c landed) total # orbits = 233 Science observation objectives throughout the mission were intimately tied to the effects four entities: 1) latitude of the sun, 2) inclination of the spacecraft orbit relative to Eros equator, and 3) radius of the orbit, and 4) Eros spin. It's very important to keep the definitions separate in your mind. Latitude of the sun tells you what parts of Eros may be illuminated. It varied slowly over the course of the orbital mission (from north to south). Mission observation phases such as 200km North, or 100 km South refer to times in the mission when the northern or southern hemisphere was illuminated, respectively. Inclination of the spacecraft orbit relative to the equator of Eros tells you what latitudes on the surface are viewable during each orbit. As a result of orbital inclination, the sub-s/c latitude varies sinusoidally throughout each orbit. Meanwhile the asteroid is of course spinning on it's axis once every 5.27 hours, bringing new longitudes into view at those general latitudes. 'Observation names' will often refer to 'north' or 'south' this or that. This refers to sub-s/c latitude, and hence latitudinal viewing.