PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = "NULL" OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "IRSN" INSTRUMENT_ID = "IRPHOT" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "IHW INFRARED PHOTOMETRY DATA" INSTRUMENT_TYPE = "INFRARED PHOTOMETER" INSTRUMENT_DESC = " Instrument Overview =================== In early discussions about plans for comet Halley observations, many observers put a high priority on systematic measurements of the infrared fluxes. Objectives included study of the evolution of the coma and tail, and of spectral features such as the silicate emission near 10 microns. Several groups organized monitoring programs at major observatories. The larger ones were at the European Southern Observatory (ESO), the Gornergrat Infrared Observatory (TIRGO), the NASA Infrared Telescope Facility (IRTF), the O'Brien Observatory (Minnesota), the South African Astrophysical Observatory (SAAO), and the United Kingdom Infrared Telescope (UKIRT). Additional programs were organized at Beijing Astronomical Observatory, Cerro Tololo Inter-American Observatory (CTIO), Haute-Provence Observatory (OHP), Kitt Peak National Observatory (KPNO), Sternberg State Astronomical Institute, and Yunnan Observatory. Individual contributions by a number of observers added to the total. Infrared filters were a difficult issue. Discussions with observers led us to conclude that for several reasons it was impractical to arrange for a dedicated infrared filter set for the comet Halley observations. First, the observatories had their own filters in multipurpose instruments that could not be modified for comet observations. Second, emission lines do not dominate the comet infrared spectrum so that filter passband locations are less critical than in the visible spectral region. Third., sub-percent precision infrared photometry of comets is currently not a high priority, and fourth, the standard (JHKL, etc.) system had been used in previous comet observations. Consequently, we recommended that the standard system be used in the near infrared observations. Unfortunately, in some instances filters in the JHKL set differ among observatories, and transformations must be worked out (cf. Tokunaga 1987, Hanner and Tokunaga 1991). On the other hand, several observatories used nearly identical filters from a set manufactured by the Optical Coatings Company and described in the Infrared Stock Filter Catalog (Optical Coatings Laboratory, Inc., Santa Rosa, California, 1987). To try to ameliorate the problems caused by non-standard filters, we put information, including transmission curves, into the archive. A related problem is that of standard stars in the infrared. Here, too, we need more standardization and precision. Hanner and Tokunaga (1991) discuss these issues in a review paper about infrared techniques and comets. The Infrared Studies Network purchased and distributed long wavelength filters centered at 18.0, 20.0, and 22.0 microns because bandpass filters at these wavelengths were not available. Sets were sent to CTIO, IRTF, KPNO, MSFC, and the University of Minnesota. Unfortunately, purchasing delays held up the filters until after Halley's perihelion. As far as we are aware, only observers at the IRTF used them to observe comet Halley. We hope that the filters will be useful in future comet observations. When requested to or when it appeared useful, we supplied ephemerides, comet news, or information on parallel observing programs to the observers. We used the electronic mail networks, the Arizona State message board, and written communications, but telephone calls had the most impact. There was less interest in coordinating observations with different techniques and at different wavelengths than we expected. For example, there was not, as far as we can tell, much coordinated visual and infrared monitoring. It is not clear how much of scientific value was actually lost by this. On the other hand, there was extensive infrared coverage on the Halley Watch days and near the encounter times of the Giotto and VEGA spacecraft. Details on the instrument system are given in the table below: Sub-Discipline: PHOTOMETRY (IRPH) ___________________________________________________________ SYSTEM OBSERVATORY INSTRUMENT TELESCOPE ___________________________________________________________ 25001600 NASA KAO UNIV. OF TEXAS 6-CHANNEL 0.9-M FAR-IR PHOTOMETER 25110500 OHP INSB PHOT 0.80-M 25001800 TIRGO INSB PHOT 1.5-M 25002400 STERNBERG INSB PHOT 1.25-M 25000500 KAVALUR INSB PHOT 1-M 22860100 YUNNAN INSB PHOT 1.1-M 23240300 BEIJING INSB PHOT 1.26-M 25680300 NASA IRTF INSB PHOT 3-M 25680100 UKIRT UKT9 IR PHOT 3.8-M 26950400 KPNO OTTO 1.3-M 26960100 WHIPPLE MMT IR PHOT 4.5-M 26860100 STEWARD CVF, AS-DOPED SI DETECTOR 1.52-M 28070100 CTIO CTIO D3 PHOT 4-M 28070200 CTIO CTIO D3 PHOT (INSB PHOT) 1.5-M 28090100 ESO IR PHOT 3.6-M 28090400 ESO IR PHOT 1-M 25001300 SAAO MK II IR PHOT 0.75-M __________________________________________________________ Scientific Objectives ===================== In the early 1980's, infrared studies of comets were still a relatively young field although observations had been made in the previous one and a half decades. These included broad-band photometric measurements, selected intermediate-resolution spectroscopy (resolving powers of 50-100), and some spatial measurements of infrared emission from the coma and tails (Wilkening 1982). The observations had established a base of information on the infrared properties of comets (primarily dust) by 1982 when the IHW was organized. The number of telescopes with infrared capability and the number of infrared astronomers had increased about tenfold in the previous decade, and infrared instrumentation had dramatically advanced. Thus it was clear that a concerted effort of infrared observations of comet Halley could help us learn much about comets. The IHW assigned all infrared (loosely defined as 1-1000 microns) observations to the Infrared Studies Network. This meant that the IR Network had to deal with photometry, spectroscopy, polarimetry, and imaging. Obviously, these areas had somewhat different goals and problems, which were reflected in the organization of the observations and the data archiving. Relatively few infrared astronomers had observed comets extensively before the IHW. This put demands on them to become familiar with the issues and methods of cometary science, and sometimes raised questions about observing techniques (fortunately only rarely after the fact). Of course, it was an objective of the IHW to advocate and encourage comet science, and maybe we succeeded. Probably, however, comet Halley itself and the accompanying excitement deserve most of the credit for the present interest in comets. Some of the data will probably not appear elsewhere, but much of the material has been published in some form in the scientific literature. However, even for published material, the archive often contains unique data or information. For example, some observers chose to publish averaged magnitudes or fluxes of several observations taken in a night. When the data were available, the archive includes all the measurements rather than just the averaged values. The archive also provides information about apertures, filters, air masses, and miscellaneous material that might not be published. When photometry data appeared in the literature and the authors submitted nothing to the IHW (a few cases), we entered the published data to make the archive as complete as possible. In all these cases, the archive files contain the references. Polarimetry files follow the same format as photometry, that is, ASCII tables with wavelength (filter), polarization magnitude, polarization direction, and ancillary information. Most of the data do not appear in digital form in the published literature. The spectroscopy and imaging files are usually in the STANDARD format FITS files. Since published spectroscopy and image data appear largely in graphical form, the digital data in the archive are the unique resource in most cases. Many image data sets contain calibration images and comparison star information. To make the archive as complete as possible, we created files for those dates when we knew of scheduled observations, even if we could not get the data. These files contain keyword information and references to assist archive users in tracking down material. The amount of missing material known to us is small (a few percent of all the data taken, including photometry, spectroscopy, and imaging). Of course, published material is not lost. However, the data in digital form that the archive contains will be a resource for future researchers. We urge those who did not submit their data to consider publishing them in extended form or including them in the Planetary Data System Archive. The result is nearly 600 files including the filter files. We estimate, however, that all of it will occupy only about 1% of the space of a compact disk." END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "HANNER&TOKUNAGA1991" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "JPL D-400-450" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "TOKUNAGA1987" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "WILKENING1982" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END