LARGE-SCALE PHENOMENA NETWORK I. INTRODUCTION In order both to conduct a second trial run and to support the 1985 September 11 encounter of the International Cometary Explorer (ICE) with Peri- odic Comet Giacobini-Zinner (G-Z), the International Halley Watch was broadened in scope to include observations of G-Z. For most of the IHW networks, the observation interval was limited essentially to 1985 July-September. Supporting the ICE mission was an especially important activity for the Large-Scale Phe- nomena Network (LSPN) because the spacecraft was being targeted to pass through the comet's plasma tail; observations of the length, width, and variability of the tail via wide-field photography were seen to be important to a full inter- pretation of the in situ data. The ICE mission was successful in nearly every sense, as the plasmas and magnetic fields were measured directly for the first time in any comet (Bame et al. 1986; Smith et al. 1986; also see Brandt et al. 1985, von Rosenvinge et al. 1986). Remote data of several types taken near and at the time of the encounter not only helped planners make late changes to the mission profile during the final approach to encounter on 1985 September 11, but also assisted scientists in the post-encounter analysis of the spacecraft observations. An example of the latter is that the width of the so-called plasma sheet measured by ICE was found to correspond approximately to the tail width observed in ground-based images and spectrograms (Slavin et al. 1986; Meyer-Vernet et al. 1986), thereby confirming the idea of cometary plasma tails as visible manifestations of the plasma sheet, and not the much broader ensemble of magnetic lobes (with embedded plasma sheet). An example of pre-encounter support was provided by IUE: observations of the comet's gas production rate in the weeks before encounter by M.F. A'Hearn and colleagues allowed calculations of the expected size of the bowshock. These values were then used by mission controllers to ensure that the Deep Space Network (DSN) was operating at the theoretical shock-crossing times. These are but two examples which illustrate the synergism which often operates between in situ and remote data. The purpose of this overview is to describe the content of the Large- Scale Phenomena (L-SP) Giacobini-Zinner archives--printed and digital CD-ROM (compact disk, read-only memory)--assembled from observations made by the LSPN Observers. Sections I-IV were written by M.B. Niedner, and Section V by A. Warnock and Niedner. II. OBSERVATIONS OF COMET GIACOBINI-ZINNER BY THE LARGE-SCALE PHENOMENA NETWORK Table I lists the L-SP Discipline Specialist personnel who made essenti- ally full-time contributions to the G-Z archive for a period of a year or more; others are thanked in the acknowledgement section at the end of this overview. The team received 118 wide-field images of G-Z from 9 different observing sites. The images are of all types--glass plates, film copies, prints, and slides--and were taken on 36 nights between 1985 July 8 and September 26. Information about the observers, instruments (including their aperture, type, f ratio and scale), and observatories (including their system codes; cf. Sec. III below) is listed in Table II. The numbers of images per UT day are given in Table III. Table I. Discipline Specialist Team of the Large-Scale Phenomena Network ________________________________________________________________________________ Team Member Affiliation Responsibility ________________________________________________________________________________ Malcolm B. Niedner, Jr. Laboratory for Astronomy Discipline Specialist and Solar Physics (LASP) NASA-Goddard Space Flight Center (GSFC) Greenbelt, MD 20771 U.S.A. John C. Brandt Laboratory for Atmospheric Discipline Specialist and Space Physics University of Colorado Boulder, CO 80309 U.S.A. Juergen Rahe Dr. Remeis Sternwarte Discipline Specialist Universitat Nurnberg-Erlangen D-8600 Bamberg Federal Republic of Germany Daniel A. LASP Senior Team Member Klinglesmith III NASA-GSFC Archibald Warnock III ST Systems Corporation Senior Software Lanham, MD 20784 Specialist U.S.A. Barbara B. Pfarr ST Systems Corporation Archive Manager Nancy E. Podger ST Systems Corporation Software Assistant Joan E. Isensee ST Systems Corporation Data/Software Assistant Steve B. Howell ST Systems Corporation Software Assistant Edwin J. Grayzeck, Jr. Interferometrics, Inc. CD-ROM Specialist Vienna, VA 22180 U.S.A. ________________________________________________________________________________ Table II. Observer List by Observatory, Telescope Parameters, and System Codes ________________________________________________________________________________ Observatory Telescope Longitude Latitude Observer(s) [deg/min/s] [deg/min/s] ________________________________________________________________________________ Hoher List Obs. 30 cm Astrograph 006/50/58 +50/09/47 Geffert, M. Hoher List f/5 Fed. Rep. of Germany 137 arcsec/mm SYSTEM = 30170300 National Astr. Obs. 70 cm Schmidt 024/43/30 +41/43/00 Ivanova, V., Rojen f/2.8 Shkodrov, V. Bulgaria 120 arcsec/mm SYSTEM = 35000301 Chorzow Obs. 20 cm Astrograph 018/59/30 +50/17/33 Wlodarczyk, I. Chorzow f/5 Poland 206 arcsec/mm SYSTEM = 35530100 Joint Obs. for 36 cm Schmidt 252/48/41 +33/59/06 Arnold, G. Comet. Res. f/2 Bair, L. Socorro, NM 298 arcsec/mm Brandt, J. U.S.A. Marr, E. SYSTEM = 37020100 Moore, E. Niedner, M. E. E. Barnard Obs. 30 cm Schmidt 254/37/30 +39/52/30 Emerson, G. Golden, CO f/1.8 U.S.A. 380 arcsec/mm SYSTEM = 35001604 A. J. Dyer Obs. 60 cm Schmidt 273/11/41 +36/03/09 Heiser, A. Nashville, TN f/3.5 U.S.A. 99 arcsec/mm SYSTEM = 35001601 Goddard Research 20 cm Cel. Schm. 283/10/23 +39/01/16 Niedner, M., Laboratory f/1.5 Schmidt, R. Greenbelt, MD 680 arcsec/mm U.S.A. SYSTEM = 35001610 Mt. Cuba Astr. Obs. 61 cm Baker Cam. 284/21/59 +39/47/04 Buckley III, J. Greenville, DE f/4 Buckley Jr, J. U.S.A. 85 arcsec/mm Sharp, W. SYSTEM = 37880100 Westergard, B. Calar Station 80 cm Schmidt 357/27/50 +37/13/45 Kohoutek, L. National Astr. Obs. f/3 Calar Alto Mt. 86 arcsec/mm Spain SYSTEM = 34930200 ________________________________________________________________________________ Table III. Distribution of Images by Day ________________________________________________________________________________ Date Number of Date Number of Date Number of Date Number of 1985 UT Images 1985 UT Images 1985 UT Images 1985 UT Images ________________________________________________________________________________ Jul. 8 1 Aug. 17 3 Sept. 8 2 Sept.17 4 12 2 21 1 9 5 18 4 13 6 22 3 10 1 19 1 17 2 23 3 11 5 20 2 19 1 24 2 12 4 21 1 20 2 27 1 13 7 22 1 25 5 Sept. 5 7 14 3 24 3 Aug. 8 1 6 8 15 2 25 1 13 1 7 9 16 13 26 1 ________________________________________________________________________________ Considering that the L-SP Network is comprised of over 100 observato- ries, the image yield was not very high for G-Z, but this was perhaps not un- expected. In a comparative sense, Giacobini-Zinner was not a bright or large- scale phenomena object, but on many dates it did possess a detectable plasma tail. Although week-to-week differences were seen in the length and brightness of the plasma tail--differences which seemed to follow the overall trend of the gas production rate--it is also true that G-Z was not observed (and was not expected) to display any of the rapid plasma-tail changes, such as disconnection events, folding tail rays, etc., which characterize the brighter comets and which make dense coverage absolutely essential for studying them. Taken in this context, we feel that the L-SP Network's response to the G-Z opportunity was excellent, and that the G-Z archive contains a useful body of data for scien- tific purposes. III. ORGANIZATION AND CONTENT OF THE PRINTED ARCHIVE Contained in the printed version of the G-Z archive is a one line table- format summary for each of the 118 images received by the L-SP Discipline Spe- cialist Center and an annotated hardcopy image for 23 of the observations. For each image the parameters listed are shown in Table IV. Table IV. Entries in the Printed Archive ________________________________________________________________________________ Heading Description ________________________________________________________________________________ Date(UT) Date (day & fraction of day) of middle of observation LSPN# Large-Scale Phenomena Network number--a unique number for each observation. (The lead digit 3 indicates that the Discipline is Large-Scale Phenomena) PlateID ID number provided by the submitting observatory on the original plate jacket or reverse side of print Ap Telescope aperture size [m] Scale Scale of the original plate [arcsec/mm]. For copy prints submitted by observers, the scale is that of the original plate, not of the print Instrument Type of instrument used FOV Field of view of the original plate [deg]. For copy prints submit- ted by observers, the listed FOV is that of the original plate, not of the print ExpM Exposure time [min] Emul Type of emulsion used for original image Filter Type of filter used Hyp Plate hypersensitization (Y or N) Cal Calibration data accompanying the image (Y or N) St Status of image. A (for Archive) indicates that the image was di- gitized and is included in the CD-ROM video archive. DS (for Discipline Specialist) indicates that the image was not scanned, but that the DS either has the original plate, a film copy, or a photographic print System Observatory System Code (see Table II and general appendix listing system codes for all networks) Observer(s) Name(s) of the observer(s) ________________________________________________________________________________ For the most part, the hardcopy images in the printed archive are of original plates and films which were scanned and deposited on the CD-ROM. There are exceptions, however: several of the prints received showed more of the comet than some of the scanned plates, and were included in hardcopy form to illustrate the state of comet Giacobini-Zinner during important times. Moreover, mostly for practical reasons, several of the scanned images do not have hardcopy representations in the printed archive. It is hoped that this slight deviation from one-to-one between the scanned images and the hardcopy photographs in the printed archive will not cause confusion. A quick check of each hardcopy LSPN# in the table will show whether the original image was scanned (St = A) or not (St = DS). The hardcopy images were generated from film copies made of the original glass plates or prints; none are hardcopy of actual digital images. The distance scale below each image equals the angular length on the sky of the quoted linear distance along the prolonged radius vector (PRV). In other words, the scale provides approximately correct distances along the plasma tail, and not in the sky plane (at the distance of the comet). IV. ORGANIZATION AND CONTENT OF THE DIGITAL (CD-ROM) ARCHIVE A. Scanning Criteria at the L-SP Discipline Specialist Center Although the total number of G-Z images was not large, careful consideration was still given to which plates and original film copies were to be digitized, because scanning time for G-Z was in a very real sense competition for the much larger set of Halley imagery. The selection criteria were: plate quality, date of observation, and UT day fraction. The first of these is obvious, the rationale for the last two being the desire to have reasonably good day-to-day coverage, and no more than two images on any given day, separated by at least 12 hours (since the comet was slowly-varying). The selection of images to be scanned was made by M.B. Niedner. Application of the scanning criteria to the entire set of glass plates and first generation film copies resulted in 24 digitized images of comet Giacobini-Zinner spanning 1985 July 20-September 26. The remaining 94 images were either unscanned (failing one or more of the 3 criteria) or unscannable (e.g., photographic prints). As a result of both the criteria tests and the temporal unevenness of network submissions, coverage in the scanned images is not as dense around the time of encounter as had been hoped. For details on the actual microdensitometer procedures used on the G-Z images, consult Sec. V. In the event that users of the CD-ROM archive have a need for additional digitized plates, it is worth noting that, unless it has been otherwise agreed to, the original glass plates will have been returned by the DS to the observers who obtained them. Given that this is the most probable situation, it would be most efficient to first contact the observer. If the plate is residing at the DS Center indefinitely, the DS would in most instances be able to digitize the image and supply it to the user on magnetic tape. B. Scanned L-SP Images of Giacobini-Zinner on CD-ROM The scanned L-SP images of comet Giacobini-Zinner were deposited on CD-ROM as three separate files: a PDS (= Planetary Data System) label, a FITS (Flexible Image Transport System) header, and the actual binary image data. The PDS label is a relatively short (10-15 lines) "header" which allows users with PDS software (e.g., IMDISP; ref: IMDISP User's Manual, M. Martin et al., JPL) to access the image data with a personal computer. The FITS header, a sample of which is given in Table V, contains all the "data about the data", and allows the user to access the image with large astronomical data packages such as AIPS and IRAF. It should be noted that the image data files have been compressed using a previous pixel algorithm. An algorithm for decompressing the images is included on the CD-ROM in pseudo-code, and a hardcopy listing is published in the printed archive. Table V. Sample FITS header for Large-Scale Phenomena ________________________________________________________________________________ Keyword Content Explanation ________________________________________________________________________________ SIMPLE = T / Basic FITS format BITPIX = 16 / 2-byte two's compl integers NAXIS = 2 / Number of axes, 2 = single image, 3 = multiple NAXIS1 = 1024 / Pixels per row NAXIS2 = 1024 / Lines per image OBJECT = 'P/GIACOBINI-ZINNER' / Name of object (on some files: 'P/G-Z ') FILE-NUM= 300305 / Number of file sent to JPL, dnnnnn DATE-OBS= '21/09/85 ' / Date of mid-exposure, dd/mm/yy TIME-OBS= 0.05199 / Time of observation, day fraction DATE-REL= '04/06/87 ' / Data release date, dd/mm/yy DISCIPLN= 'LARGE SCALE PHEN ' / IHW Network LONG-OBS= ' 24/43/30 ' / Station longitude ddd/mm/ss (positive to east) LAT--OBS= '+41/43/00 ' / STATION latitude sdd/mm/ss (s = + or -) SYSTEM = '35000301 ' / Observing system code OBSERVER= 'IVANOVA,V/SHKODROV,V ' / Name(s) of observer(s) SUBMITTR= 'NIEDNER,M ' / LSPN submitter SPEC-EVT= F / Special events flag DAT-FORM= 'STANDARD ' / Standard FITS data DAT-TYPE= 'IMAGE ' / Type of FITS data LSPNSEQ = 194331 / Sequence # of plate received at L-SP Center COMMENT COMMENT / Submitting station OBSVTORY= 'NATIONAL AST. OBS.' / Name of observatory LOCATION= 'ROJEN, BULGARIA ' / Station location--address COMMENT COMMENT / Instrument specifications TELESCOP= 'SCHMIDT ' / Type of telescope APERTURE= 0.700 / Telescope aperture [m] FRATIO = 2.800 / Effective telescope f ratio FOV1 = 5.000 / R.A. field of view [deg] FOV2 = 5.000 / Dec field of view [deg] COMMENT COMMENT / Plate specifications PLTSZE1 = 0.160 / X plate size [m] PLTSZE2 = 0.160 / Y plate size [m] PLTSCALE= 121.112 / Plate scale [arcsec/mm] CALAVL = T / Calibration available HYPSEN = F / Hypersensitization EMULSION= 'IIIA-J ' / Emulsion type FILTER = 'M ' / Type of filter used PLTYPE = F / Plate type, T = original, F = copy COMMENT COMMENT / Observation specifications EXPOSURE= 1800. / Exposure time [s] HISTORY OBSLOG = '2850 ' / Original observatory plate HISTORY CMTS-LOG= 'COMET IS FAINT; TAIL IS BROAD AND DIFFUSE, PROBABLY DUST. ' COMMENT COMMENT / Tape specifications BSCALE = 1.0 / Scale factor, TRUE = TAPE * BSCALE + BZERO BZERO = 0.0 / Offset for true pixel value BUNIT = 'DENSITY ' / Units of pixel values BLANK = -32767 / Value for undefined pixel COMMENT COMMENT / Digitization specifications HISTORY SCNAPR = 20 / PDS scan aperture [micron] HISTORY SCNSTP = 20 / PDS scan step [micron] HISTORY SKYDEN = 412 / Sky background PDS density HISTORY SKYUNF = 'FAIR ' / Sky background: POOR/FAIR/GOOD/EXCL COMMENT COMMENT / Astrometry information EQUINOX = 1950.0 / Equinox of coordinate system CTYPE1 = 'RA---ARC ' / X axis units CTYPE2 = 'DEC--ARC ' / Y axis units RA--CPME= 0.961125E+02 / R.A. plate center mid-exposure DEC-CPME= 0.102762E+02 / Dec plate center mid-exposure CRPIX1 = 0.600200E+03 / Reference point for AXIS1, samples CRPIX2 = 0.263250E+03 / Reference point for AXIS2, lines CDELT1 = -0.672847E-03 / R.A. per pixel [deg] CDELT2 = -0.672847E-03 / Dec per pixel [deg] CROTA1 = 0.317443E+00 / Rotation angle in R.A. [deg] CROTA2 = 0.317443E+00 / Rotation angle in Dec [deg] SENSE = T / Sense of rotation, T=counterclws., F=clockwise CRVAL1 = 0.961125E+02 / R.A. at reference point [deg] CRVAL2 = 0.102762E+02 / Dec at reference point [deg] RA--HEAD= 0.961554E+02 / R.A. of comet head at mid-exposure [deg] DEC-HEAD= 0.101321E+02 / Dec of comet head at mid-exposure [deg] COMMENT COMMENT / Processing and analysis information DATE-REC= '04/06/87 ' / Date plate was received at GSFC, dd/mm/yy HISTORY DATE-PDS= '29/03/88' / Date of plate digitization, dd/mm/yy HISTORY DATE-PRC= '04/04/88' / Date processed/calibrated, dd/mm/yy QUALITY = '2222 ' / Quality of plate,guiding,trails,seeing,transp. HISTORY CONVERTED TO FITS BY PROGRAM IHWP2F WED APR 06,1988 HISTORY PDS OPERATOR'S COMMENT FOLLOWS: HISTORY 880329 ID194310 S200 A20 L1024 P1024 END ________________________________________________________________________________ The meaning of the FITS keywords is fairly straightforward in the exam- ple header given (see text descriptions to the right of the / in each line), and most will not be belabored here. Many of the keywords near the top of the header--BITPIX, NAXIS, NAXIS1, NAXIS2, etc.--are standard, mandatory keywords which have been described by Wells et al. (1981). The reader is referred to that paper for further details. DATE-REL was originally intended to give the earliest possible release date for imagery contributed by network members, but is now irrelevant since the archive is complete and is being distributed. The SYSTEM code denotes the ob- servatory and the instrument used to obtain the image; refer to Table II and to the general appendix listing for this information for all disciplines. SPEC-EVT has been set = F for all the G-Z images because nothing truly outstanding was apparent in any of them. [In Halley, disconnection events, bursts of ray generation, and major distortions of the plasma tail merit the designation SPEC-EVT = T, but none of these were seen in G-Z]. PLTYPE designates whether the image was an original or a copy made by the contributing observer. In some cases, when the observer sent the DS a high quality film copy only, it was possible to scan that copy. The history keywords OBSLOG, CMTS-OBS, and LSPN-OBS give the observatory plate ID, observer comments, and Discipline Specialist assessment of the image, respectively. Most of the keywords in the astrometry section have names and meanings identical to keywords defined by Wells et al. (1981), but in accordance with their strong suggestion, the uses and conventions of CROTA1, CROTA2, and SENSE will be defined precisely here. All three keywords refer to the rotation of the X-Y PDS (microdensitometer) coordinate frame relative to the axes of the celestial coordinate system. To reasonable accuracy, the +Y scanning axis is in the direction of North at the plate center, for the epoch of 1950.0. The +X scanning axis is in the approximate direction of due East (again, at the plate center for 1950.0). As a result of the inevitable human error in positioning the plate on the PDS platen, however, there will be a non-zero rotation angle offset (very small) between the two coordinate systems. When the North direction lies in the +X/+Y quadrant, i.e., is rotated in a counterclockwise direction relative to the +Y axis, we say that the rotation angles CROTA1 and CROTA2 are both positive (and of the same value). A positive angle for such a counterclockwise rotation is what is meant by SENSE = T (check the text to the right of the SENSE keyword). It will be noted from the values of RA-CPME, DEC-CPME, CRVAL1, and CRVAL2 in the sample header, that we define the reference point on the plate to be the tangent point or plate center. The coordinates for the approximate comet head center are given by RA-HEAD and DEC-HEAD except when the scanned plate is an offset plate and the head is not present on the plate; in this case these keywords are simply dropped from the header. Note that the head center coordinates are for reference purposes only and are not to be used for accurate positions of the nucleus; well-saturated, wide-field plates are certainly not suitable for that purpose! The QUALITY keyword gives a very subjective assessment of the condition of each scanned image in terms of five categories (plate, guiding, trails, seeing, and transparency); the scale is 1-5 (excellent to poor). C. Dataless Headers (Unscanned Images) Ninety-four of the images received by the L-SP Center were not scanned, but FITS headers have been generated for them as well, and they reside on the CD-ROM. These headers contain a subset of the keywords listed above, mostly those which describe platelog parameters (date, emulsion, filter, exposure time, etc.). V. PROCEDURES FOR DIGITIZING PLATES A. Plate Materials Most of the submissions to the Large-Scale Phenomena Discipline were in the form of photographic plates or films. Original glass plates or film were most desirable for digitizing, but first generation film copies were also acceptable. Original plates were digitized whenever possible according to the scanning criteria outlined earlier, in Section IV.A. B. Hardware All digital images produced by the Large-Scale Phenomena DS Team were generated on one of the two Perkin-Elmer PDS 1010A Microdensitometers (PDSs) in the Laboratory for Astronomy and Solar Physics at GSFC. The PDSs have been modified to enhance performance by replacing the original logarithmic amplifier circuit with a faster one (Anderson et al. 1983), and replacing the original analog-to-digital converter with one which provides a sample-and-hold circuit in support of the faster log amplifier. Each PDS is controlled by a DEC PDP-11/23 minicomputer running version 5.1 of the RT-11 operating system. The PDS is interfaced to the computer through a bus converter board that allows the Unibus interface of the PDS to operate on the Q-bus of the PDP-11/23. The control programs were written in a combination of Fortran IV and PDP-11 assembly language. All scanning was performed with the microdensitometers in density mode. The optical system of the microdensitometer passes a beam of light through a pre-slit aperture which defines the size of the scanning spot. The beam is focused on the plate, then passes through a post-slit and a Fresnel lens to illuminate a photomultiplier tube. The output voltage from the photomulti- plier tube is sent to a logarithmic amplifier, yielding an approximate photo- graphic density. The output voltage from the log amplifier is converted into PDS density units by a a 10-bit analog-to-digital converter. The plate is scanned by moving the PDS platen, under computer control, in a raster pattern. As the plate is passed through the light beam, the photomultiplier voltage is read at each pixel in real time. The digital images were written in a PDS line-by-line format to magnetic tape at 1600 bpi on Kennedy 9000-series dual density (1600/800 bpi) tape drives. The PDS format tapes were converted to FITS format on the IBM 3081 mainframe at Goddard, then checked for readability and accuracy on a VAX 11/750 computer in the LASP before submission to the Lead Center. C. Preliminary Procedures Before scanning a plate, the microdensitometer was used as a measuring engine to produce an astrometric solution for the entire plate. The astrometry program assumes a Schmidt plate geometry, using the transformation equations given by Dixon (1962). The assumption of Schmidt plate geometry yields acceptable results even for plates from other types of telescopes. Reference stars were selected from the AGK3 catalog for plates north of -5 deg declination. The Perth-70 catalog was used for southern declinations. Although the SAO catalog is generally unacceptable for astrometric work, it was occasionally used when none of the other catalogs yielded an adequate number of reference stars to get a satisfactory plate solution. The software corrects for proper motions from the catalog date to the plate epoch, and precession may be performed to any desired date. All positions are given in 1950.0 coordinates. Mean astrometric error depends strongly on the individual plate scales and somewhat on the number of acceptable reference stars available, but is typically less than 10 arcsec (worst case) and frequently is on the order of 2 to 5 arcsec. The plate solution was used to measure the rotation angle of the North-South meridian passing through the plate center, relative to the Y-axis of the microdensitometer. The coordinates of the comet's head center were also calculated, although this manual measurement provides only a crude location for the nucleus embedded in a highly-saturated coma. D. Scanning After completion of the astrometry, the region of interest on the plate was scanned. The aperture size was selected to yield roughly the same angular resolution per pixel, regardless of the original plate scale. Typically, an aperture of 40 or 50 microns was used on plates with plate scales around 100 arcsec/mm, and an aperture of 10 or 20 microns was used for plates with scales greater than about 200 arcsec/mm. Spatial resolution of the photographic emulsions limits the smallest usable apearture to 5 or 10 microns in any event. Generally, the step size was equal to the aperture size, so the pixels were contiguous across the scan line with no oversampling. The photomultiplier tube high voltage was set to yield 0 density on clear glass, when clear glass was available. Otherwise, the density was set to around 0.1D on the background fog, primarily to avoid negative density values in the resulting digital image. The 10-bit analog-to-digital converter yields integers in the range 0 to 1023. These may be converted to an approximate photographic density by dividing by 200. ACKNOWLEDGEMENTS Without the diligent efforts of LSPN observers to obtain and submit observations of comet Giacobini-Zinner, these printed and CD-ROM archives for Large-Scale Phenomena would not have been possible, at least not in their existing substantial form. It is a pleasure for the Discipline Specialists to thank each and every contributing L-SP Network Observer both for submitted observations of Giacobini-Zinner, and of Halley. We are very hard at work on the latter archives at the moment, and think that when it is finished it will speak extremely highly of the cooperation of astronomers worldwide. Contributors to the L-SP Discipline effort who are not listed in Table I, but who strongly deserve recognition as well as our thanks are: L.L. Taylor, M.R. Greason, K. Bhagat, J. Gagliardi (all of ST Systems Corporation), J. Sinclair (Royal Greenwich Observatory, Hailsham, East Sussex, U.K.), W. Liller (Instituto Isaac Newton, Vina del Mar, Chile), and P.D. Usher (Pennsylvania State University, University Park, PA 16802, U.S.A.). J.C. Brandt and M.B. Niedner would like to express their thanks to E.P. Moore of the Joint Observatory for Cometary Research (JOCR), Socorro, NM 87801, U.S.A., for his hospitality during a run at JOCR in September 1985 observing G-Z days after the historic ICE encounter and during the G-Z/Halley conjunction. REFERENCES Anderson, C., Slovak, M.H., and Michalski, D.E. (1983). In Astronomical Micro- densitometry Conference, NASA CP-2317, edited by D.A. Klinglesmith (U.S. GPO, Washington, DC), p. 163. Bame, S.J., Anderson, R.C., Asbridge, J.R., Baker, D.N., Feldman, W.C., Fuselier, S.A., Gosling, J.T., McComas, D.J., Thomsen, M.F., Young, D. T., and Zwickl, R.D. (1986). Science 232, 356. Brandt, J.C., Niedner, M.B., Jr., and Farquhar, R.W. (1985). Advances in Space Research 5, No. 12, p. 3. Dixon, M.E. (1962). Mon. Not. R. Astron. Soc. South Africa 21, 180. Meyer-Vernet, N., Couturier, P., Hoang, S., Perche, C., and Steinberg, J.L. (1986). Geophys. Res. Lett. 13, 279. Slavin, J.A., Goldberg, B.A., Smith, E.J., McComas, D.J., Bame, S.J., Strauss, M.A., and Spinrad, H. (1986). Geophys. Res. Lett. 13, 1085. Smith, E.J., Tsurutani, B.T., Slavin, J.A., Jones, D.E., Siscoe, G.L., and Mendis, D.A. (1986). Science 232, 382. von Rosenvinge, T.T., Brandt, J.C., and Farquhar, R.W. (1986). Science 232, 353. Wells, D.C., Greisen, E.W., and Harten, R.H. (1981). Astron. Astrophys. Suppl. 44, 363.