PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM RECORD_BYTES = 72 FILE_RECORDS = 25993 ^SPREADSHEET = "SDCRAM.CSV" DATA_SET_ID = "NH-X-SDC-3-KEMCRUISE1-V1.0" INSTRUMENT_HOST_NAME = "NEW HORIZONS" INSTRUMENT_HOST_ID = "NH" INSTRUMENT_NAME = "STUDENT DUST COUNTER" INSTRUMENT_ID = "SDC" PRODUCT_NAME = "SDCRAM" PRODUCT_CREATION_TIME = 2019-04-04T00:00:00 START_TIME = 2015-01-01T00:00:00 STOP_TIME = 2017-12-18T23:59:58 DESCRIPTION = " The Comma-Separated Values (CSV) file provides a broad summary of the attitude of the New Horizons (NH) Student Dust Counter (SDC) boresight with respect to the ram (velocity) direction, along with a summary of when the SDC instrument was on. Some users may be interested in the angle between the boresight and the Sun-relative NH position vector. Such users should note that the angle between the velocity and ram directions was small for most of the mission after Jupiter encounter, and less than twenty degrees since late 2008. So this table can also serve as a reasonable proxy for the angle between the Sun-relative NH position and SDC boresight vectors. For more detailed analyses, the user is referred to the PDS NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0]. Also note that the Sun=>NH position vector is in the PDS label for each SDC data product, along with the spacecraft attitude quaternion, relative to the J2000 reference frame. So calculation of the angle between the SDC boresight and the Sun=>NH vectors is possible and straightforward using the data in each SDC data product label. The purpose of this document is to provide PDS users with a rough guide to when the SDC instrument on the spacecraft is oriented in a way that generating dust events is possible and/or likely. In this context, there are three general attitude domains of interest during the mission: 1) Spinning modes (passive or active): the High-Gain Antenna (HGA) is pointed in the direction of Earth, so the SDC boresight, which is normal to the SDC detectors' surface and opposite to the HGA, will be pointing roughly in the direction of travel, also known as the ram direction, with respect to the Sun (assumes the Sun-Earth elongation is small). 2) Three-Axis mode while communicating to or from the Deep Space Network (DSN) on Earth. This is similar to spinning modes in that the HGA is again pointed toward Earth, and the SDC will be near the ram direction. 3) Three-Axis mode during observations. This is when the SDC is least likely to be pointed near the ram directions, as the spacecraft takes on whatever attitude is necessary for the remote instruments' observations. Refer to SDC.CAT in the CATALOG/ directory of this data set for information about the SDC instrument. Each row of the SPREADSHEET represents sixty samples taken at one per minute, or about one hour per row. On each row, there are two times, six accumulating calculations performed sixty times per row with the final accumulation for each put into the row, and two angles giving the upper and lower limits calculated over the sixty samples. 1) Two time fields (start and stop UTC) 2) Four counter fields indicating the attitude domain of the spacecraft: 2.1) 3-axis mode (angular velocity < 0.5 RPM) 2.2) Transition between 3-axis and spinning mode (0.5 to 4.5 RPM) 2.3) Spinning mode (> 4.5RPM) 2.4) A counter indicating how often the attitude check failed due to gaps in the C-Kernel coverage. 2.5) The counters can each take values from zero to sixty, and the sum of these four counters on each row will be sixty, representing the sixty samples accumulated in the row. 3) Two counter fields indicating the power state of the SDC instrument: 3.1) The number of samples for which the SDC was powered on. 3.2) The number of samples for which the SDC was powered off. 4) Two fields comprising max and min of the angle between the SDC detector normal vector and the ram direction vector, over the sixty samples. 5) Two fields comprising the range (minimum and maximum values) of the angles between the SDC detector normal vector and the ram direction vector, as calculated over the sixty samples. 5.1) The SDC detector normal vector is normal to the SDC detector surface toward the side from which incoming dust particles arrive; it is also the SDC boresight vector as defined in the NH SPICE frame and instrument kernel files. 5.2) The ram direction vector is the Sun-relative velocity vector of the spacecraft; it is independent of the Sun-relative position vector of the spacecraft. 5.3) Both the SDC boresight vector and the ram direction vector are rotated to the J2000 reference frame, and the angle between them is calculated, for each of the sixtiy samples represented by the row. The minimum and maximum angle values in those sixty samples become these two fields for the row. 5.4) If fewer than sixty samples had a successful attitude calculation, then the failure counter (2.4 above) will be non-zero, but these two fields will still contain the maximum and minimum values for the boresight-ram angles which could be successfully calculated. If no samples had a successful attitude calculation, then the failure counter will be sixty, and these maximum and minimum fields will be -999.0, which is the invalid constant (PDS keyword INVALID_CONSTANT) for these fields. As noted above, this SPREADSHEET is intended as only a rough guide to the attitude of the spacecraft during SDC observation periods. Subtleties, such as the difference between the ram direction and a vector pointing directly away from the Sun, are ignored. To fully assess the best estimate for any single event time, use the SPICE kernels in the PDS data set [NH-J/P/SS-SPICE-6-V1.0]. " OBJECT = SPREADSHEET ROWS = 25993 ROW_BYTES = 72 FIELDS = 10 FIELD_DELIMITER = "COMMA" OBJECT = FIELD NAME = "START TIME" FIELD_NUMBER = 1 BYTES = 19 DATA_TYPE = "TIME" DESCRIPTION = "This field is the UTC of the first of the sixty samples represented by the row. " END_OBJECT = FIELD OBJECT = FIELD NAME = "STOP TIME" FIELD_NUMBER = 2 BYTES = 19 DATA_TYPE = "TIME" DESCRIPTION = "This field is the UTC of the last of the sixty samples represented by the row. It will be fifty-nine minutes after the START TIME (field 1) for the row, and one minute before the START TIME of the next row. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR 3-AXIS MODES" FIELD_NUMBER = 3 BYTES = 2 UNIT = "COUNT" FORMAT = "I2" DATA_TYPE = "ASCII_INTEGER" DESCRIPTION = "This field provides the number of samples where the angular velocity of the spacecraft was less than 0.5RPM. This is assumed to be a proxy for the number of samples taken when the spacecraft was in a 3-Axis atttitude mode. The calculation of angular velocity was made using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. N.B. this counter does not distinguish between the various 3-Axis modes. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR TRANSITION" FIELD_NUMBER = 4 BYTES = 2 FORMAT = "I2" UNIT = "COUNT" DATA_TYPE = "ASCII_INTEGER" DESCRIPTION = "This field provides the number of samples where the angular velocity of the spacecraft was between 0.5 and 4.5RPM. This is assumed to be a proxy fo the number of samples taken when the spacecraft was in transition between a spinning mode and a 3-Axis mode, or vice versa. The calculation of angular velocity was made using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR SPINNING MODES" FIELD_NUMBER = 5 BYTES = 2 FORMAT = "I2" UNIT = "COUNT" DATA_TYPE = "ASCII_INTEGER" DESCRIPTION = "This field provides the number of samples where the angular velocity of the spacecraft was greater than 4.5RPM. This is assumed to be a proxy fo the number of samples taken when the spacecraft was in a spinning mode. The calculation of angular velocity was made using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. N.B. this counter does not distinguish between the various spinning modes. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR UNKNOWN ANGULAR VELOCITY" FIELD_NUMBER = 6 BYTES = 2 FORMAT = "I2" UNIT = "COUNT" DATA_TYPE = "ASCII_INTEGER" DESCRIPTION = "This field provides the number of samples where the angular velocity calculation failed, typically due to gaps in coverage by the SPICE C-Kernels. This is a normal occurrence; for example, during hibernation and passive spinning mode, attitude data are not recorded on the spacecraft. The calculation of angular velocity was made using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR SDC ON" FIELD_NUMBER = 7 BYTES = 2 DATA_TYPE = "ASCII_INTEGER" FORMAT = "I2" UNIT = "COUNT" DESCRIPTION = "This field provides the number of samples where the SDC instrument power was turned on. This field does not account for any power activities, including turning individual dust detector channels on and off, due to autonomy rules. Refer to the SDC ON/OFF tables for more detail. " END_OBJECT = FIELD OBJECT = FIELD NAME = "COUNTER FOR SDC OFF" FIELD_NUMBER = 8 BYTES = 2 DATA_TYPE = "ASCII_INTEGER" FORMAT = "I2" UNIT = "COUNT" DESCRIPTION = "This field provides the number of samples where the SDC instrument power was turned off. This field does not account for any power activities, including turning individual dust detector channels on and off, due to autonomy rules. Refer to the SDC ON/OFF tables for more detail. " END_OBJECT = FIELD OBJECT = FIELD NAME = "MINIMUM SDC BORE-RAM ANGLE" FIELD_NUMBER = 9 BYTES = 7 DATA_TYPE = "ASCII_REAL" FORMAT = "F7.2" UNIT = "DEGREES" INVALID_CONSTANT = -999.00 DESCRIPTION = "This field provides the minimum value of the angle between the SDC boresight and the ram direction. As long as one or more samples were successfully calculated, this value will range from 0.00 to 180.00. For rows ocurring during large gaps in the time coverage of the available SPICE C-Kernels, there may be no successful results, the COOUNTER FOR UNKNOWN ANGULAR VELOCITY field (FIELD_NUMBER 6) will be 60, and this field will have the INVALID_CONSTANT value of -999.00. The calculation of the boresight-ram angle using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. " END_OBJECT = FIELD OBJECT = FIELD NAME = "MAXIMUM SDC BORE-RAM ANGLE" FIELD_NUMBER = 10 BYTES = 7 DATA_TYPE = "ASCII_REAL" FORMAT = "F7.2" UNIT = "DEGREES" INVALID_CONSTANT = -999.00 DESCRIPTION = "This field provides the maximum value of the angle between the SDC boresight and the ram direction. As long as one or more samples were successfully calculated, this value will range from 0.00 to 180.00. For rows ocurring during large gaps in the time coverage of the available SPICE C-Kernels, there may be no successful results, the COOUNTER FOR UNKNOWN ANGULAR VELOCITY field (FIELD_NUMBER 6) will be 60, and this field will have the INVALID_CONSTANT value of -999.00. The calculation of the boresight-ram angle using SPICE C-Kernels; refer to the NH SPICE data set [NH-J/P/SS-SPICE-6-V1.0] for more details. " END_OBJECT = FIELD END_OBJECT = SPREADSHEET END