RADIO SCIENCE NETWORK 1. INTRODUCTION Radio Astronomy is a developing new technique for the study of comets. In some areas, such as observations of the OH radical via its 18 cm transitions, the observational procedures and analysis are well developed. Studies in these areas have proved their value since they both provide new probes of important physical processes as well as a window on physical processes which are less wellknown and less accessible to study by other techniques. In many other areas, however, the study of comets at radio wavelengths continues to be primarily an exploratory endeavor. In recognition of this fact, the IHW Radio Science Discipline Specialist team (Table I) felt that it was important to attempt many different kinds of observations during this campaign on Halley's Comet, since each observation has scientific merit as an exploration. Thus, we have been careful to document and include all data submitted to this archive by radio observers. Table I. Discipline Specialist Team of the Radio Science Network ___________________________________________________________________________ Team Member Affiliation Responsibility ___________________________________________________________________________ William M. Irvine Astronomy Program Discipline Specialist University of Massachusetts Amherst, MA 01003 U.S.A. F. Peter Schloerb Astronomy Program Discipline Specialist University of Massachusetts Eric Gerard Departement de Radioastronomie Discipline Specialist Observatoire de Meudon F-92190 Meudon France Ronald D. Brown Department of Chemistry Discipline Specialist Monash University 1981-85 Clayton, Victoria 3168 Australia Peter D. Godfrey Department of Chemistry Discipline Specialist Monash University 1981-85 Wayne M. Kinzel Astronomy Program Archive Manager University of Massachusetts ___________________________________________________________________________ 1.2 Radio Science Network Summary The P/Halley Archive contains data from 36 different observing groups, representing a range of techniques. The majority of the observational data comes in the well developed area of 18cm OH observations. However, many other projects were attempted as well. Approximately 75% of the groups who are known to have obtained useful data on the comet have submitted it to the archive, and we are grateful to them for their contributions. In this document, we describe the format of the data contained in the Radio Science archive of observations of P/Halley. In Sec. 2, we present a detailed description of the FITS files which contain the data. Section 3 contains a description of the Radio Science Index to the CD-ROM. Section 4 provides a description of the printed archive format, which may also be used as an index to the data under some circumstances. The units adopted by the Radio Science Network are given in Sec. 5, and the calibration of data is discussed in Sec. 6. Finally, in Sec. 7, we acknowledge those who have been so helpful to us in the construction of this archive. 2. THE RADIO SCIENCE FITS FORMAT 2.1 FITS Header Description The IHW Radio Science archive is written in FITS format following the standard for all networks within the IHW. FITS files are a standard for interchange of astronomical data. They consist of one or more 2880-byte header records, which contain the documentary information about the observation, followed by 0 or more 2880-byte data records in the format that is specified by the FITS header. In the IHW archive, these two parts of a FITS file, the header records and the data records, are presented in two different files to facilitate their use by a wide range of analysis software. However, we note that users who require FITS format files have only to concatenate the header and data files to make a standard FITS file. The FITS header is meant to provide a description of the structure and format of the FITS data records that follow it and to offer any auxiliary information that is necessary for its interpretation. For the Radio Science FITS header, we have defined several FITS keywords which specify observational parameters that are necessary to interpret the data. A detailed description of the complete Radio Science FITS header is presented in Sec. 2.1. In general, the Radio Science Network has tried to conform to standards which are commonly used in FITS and adopted by the IHW. The characteristics of the observation are described by assigning values to the "keywords" which are described in the tables below. We note that special keywords which we have defined have been selected to specify information which is vital to the interpretation of the data, such as specification of the observing frequncy or telescope parameters. At another level, under FITS HISTORY keywords, we present information about how the data were obtained, including calibration and orbital tracking information. The distinction between these groupings is admittedly somewhat arbitrary and has been made primarily to limit the number of new FITS keywords defined by our network. In an exploratory program, like the Radio Science Network, it is to be expected that many observations will fail to detect the comet, and the data to be archived are best described as an upper limit rather than through presentation of a spectrum or image. In recognition of this fact, the IHW permits FITS files to be created without any data records at all, and in this case, the "data" are presented as a summary in the FITS HISTORY section of the Radio Science header. FITS files of this type may be recognized because they have the NAXIS keyword set equal to 0 and the DAT-TYPE keyword set equal to the character string 'NODATA '. Where possible, even when actual data exist, we have attempted to describe them by presenting the results of a model fit to the data. In spectral line work, for example, a line is often described in terms of its peak intensity, the velocity of the peak, the line width, the integrated area under the line, and the mean velocity of the emission. We have provided these values in FITS HISTORY keywords by fitting a gaussian line shape model to the data. 2.1.1 Keyword block I: Basic FITS keywords This block of keywords is required of FITS tapes. The details are listed in Table II below. Table II. Keyword Block I ______________________________________________________________________________ Keyword Type Description ______________________________________________________________________________ SIMPLE L Conformity to basic FITS standards BITPIX I Bits per pixel in data record NAXIS I Number of axes in data record; if NAXIS = 0 then no data record NAXIS1 I Number of pixels in row along first axis; if NAXIS1 = 0 then this is Extended FITS Format and GROUP data are present NAXISn I Number of pixels along n-th axis in image ______________________________________________________________________________ 2.1.2 Keyword block II: International Halley Watch keywords These keywords are agreed upon for use by the entire Halley Watch and they are listed in Table III. Table III. Keyword Block II ______________________________________________________________________________ Keyword Type Description ______________________________________________________________________________ OBJECT C Name of the object Examples: 'P/CROMMELIN' 'P/HALLEY' 'P/GIACOBINI-ZINNER' FILE-NUM I 6NNNNV - unique, sequential number to identify files sent to IHW Lead Center. Format description: 6 = denotes Radio Science Network NNNN = unique 4 digit ID number assigned to each observation V = version number (used to keep track of resubmissions) DATE-OBS C 'DD/MM/YY' - UT date of middle of observation if observations made during several intervals, then these intervals will be specified in the HISTORY fields described below TIME-OBS R UT time of middle of observation expressed in decimal days DATE-REL C 'DD/MM/YY' - date when observations may be publicly released DISCIPLN C 'RADIO STUDIES' - the Network identification LONG-OBS C 'DDD/MM/SS' - east longitude of observatory (0-360 deg) LAT--OBS C 'sDD/MM/SS' - latitude of observatory SYSTEM C '6OOOCCTT' - system code formatted: 6 = Radio Science Network OOO = IAU number for observatory (OOO = 500 for radio observatories since no IAU number exists) CC = identifies country according to LSPN Code TT = identifies radio telescope OBSERVER C Name of observer Format : 'LASTNAME,I' - 1 author 'LASTNAME,I/NEXTNAME,J' - 2 authors 'LASTNAME,I/ET AL.' - >2 authors For more than 2 observers, the names of all additional observers are given in special ADD. OBS. comments SUBMITTR C Name of submitter of data SPEC-EVT L Flag for special events as designated by Discipline Specialist DAT-FORM C Describes format of FITS data records 'NODATA ' - no FITS data records written 'STANDARD' - data records conform to FITS standard 'ASCII ' - data records are to be interpreted as logical records of 80 ASCII characters (not FITS standard) 'HARDCOPY' - data submitted as hardcopy ______________________________________________________________________________ 2.1.3 Keyword block III: Radio Science keywords These keywords are to be directly read by computers in the normal manner of FITS header keywords. Some attempt has been made to choose keyword names that are already in use by the astronomical community. These keywords are used to describe information that is vital to the data interpretation or potentially useful for searches of the data base (Table IV). Table IV. Keyword Block III ______________________________________________________________________________ Keyword Type Description ______________________________________________________________________________ DIS-CODE C 'TFESEWEABENC' - describes parameters of the telescope/instrument T : Telescope type S = single antenna I = interferometer U = unknown/unclassified FE: Frequency (Center Frequency or Rest Frequency) FE=> frequency = F x 10**(E) MHz 00= unknown SE: Spectral resolution SE=> spectral resolution = S x 10**(E) Hz 00= unknown WE: Bandwidth WE=> bandwidth = W x 10**(E) Hz 00= unknown A : Beam description C = circular E = ellipitical O = other U = unknown BE: Beam size (geometric mean) BE=> beam size = B x 10**(E) arcsec 00= unknown N : Noise estimate N => RMS noise = 10**(N) microJansky/beam 0 = unknown C : Information provided by observer to Discipline Specialist is complete T = TRUE F = FALSE DAT-TYPE C 'NNSTHP' - describes the data format in Header and Data Records NN: Subnetwork OH= OH Subnetwork Spectral line observations of 18-cm OH SL= Spectral Line Subnetwork Spectral line observations (other than 18-cm OH) CN= Continuum Subnetwork Broadband continuum observations OC= Occultation Subnetwork Observation of occultation events RD= Radar Subnetwork Active experiments S : Search/detection status S = search - implies nondetection (< 3 sigma) D = detection - implies detection (> 3 sigma) M = marginal - implies marginal detection (approx. 3 sigma) T : Type of data in FITS Data Records N = no FITS Data Records S = Spectrum => intensity vs frequency C = Continuum scan => intensity vs space T = Time series => intensity vs time I = Image => spatial - spatial image D = Dynamic spectrum => frequency - time image F = SV image => frequency - spatial image V = Visibility Function Data H : Summary of Data in Header? T = Summary of data exists in Header History Section F = No summary of data in Header History Section P : Polarization status I = Intensity data only P = Polarization data format used OBSVTORY C Abbreviation for Observatory. TELESCOP C Telescope identifier - usually gives aperture size in meters LOCATION C Location of Observatory as given in American Ephemeris INSTRUME C 'FRONT/BACK' - describes "frontend" and "backend" of receiver FRONT: Receiver Front End MASER = Maser Amplifier FET = Field Effect Transistor Amplifier PARA = Parametric Amplifier MIXER = Mixer SPEC = Special Front End UNK = Unknown Front End BACK : Receiver Back End FB = Filterbank SEFB = Filterbank with Spectrum Expander AC = Autocorrelator CONT = Broadband Continuum Receiver SPEC = Special Back End AOS = Acousto-Optical Spectrometer UNK = Unknown Back End CENTFREQ R Center frequency of observed bandwidth (Hz) BANDWIDT R Total bandwidth (Hz) BEAMSIZE R Geometric mean of major and minor axes of Elliptical Gaussian Beam (deg) BEAMELON R Ratio of major beam axis to minor beam axis BEAMROTA R Position angle of major beam axis (deg) BEAMEFF R Beam efficiency - fraction of power received that is in the Gaussian Main Beam (BEAMEFF = 0.0 if unknown or unspecified) MOLECULE C Chemical formula for molecule (follows convention of NBS interstellar-line list) TRANSITN C Quantum numbers for transition (follows convention of NBS interstellar-line list) RESTFREQ R Rest frequency of line used by observer (Hz) RES-SPEC R Spectral resolution (Hz) - true spectral resolution of the spectrometer, NOT the channel spacing EQUINOX R Equinox of RA-DEC information presented in this file RAOFF R Pointing offset in RA direction DELTA(RA)*COS(DEC) (deg) DECOFF R Pointing Offset in Dec direction DELTA(DEC) (deg) DATE-BEG C 'DD/MM/YY' - UT date on which observations began DATE-END C 'DD/MM/YY' - UT date on which observations ended ______________________________________________________________________________ 2.1.4 Keyword Block IV: Special Keywords for Printed Archive This group of COMMENT lines give additional information to be used in the production of the IHW printed archive. The ADD. OBS. comment gives the names of the full observing team in the case that more than two observers carried out the observations. More than one ADD. OBS. comment may be used to specify teams with many members or long names. The format of the ADD. OBS. comment is: COMMENT ADD. OBS. NAME,I/NAME2,I/NAME3,I The NOTE comment provides information that is to be printed as a footnote in the printed archive in the following format: COMMENT NOTE THIS IS A TEST 2.1.5 Keyword Block V: Radio Science Data History Section This block of FITS HISTORY keywords is provided to incorporate additional information about the observation, such as descriptions of calibration methods and sources, details about observing procedures, and comments by the observer and the IHW Discipline Specialist. Another important use of the HISTORY lines is to provide a summary of the data obtained, or in the case of FITS files with no data records, the actual data values reported by the observer. The general format of the HISTORY lines is: column 1 11 21 HISTORY SUBKEY__ VALUES.... where values is a list of values associated with this subkey. In most cases, the value lists are in a fixed format in order to simplify their use. 2.1.5.1 Data summary section In order to transmit upper limits or a summary of the data that would be appropriate for tabular presentation in the printed archive, we utilize one of the following HISTORY keyword formats. Such summaries of the data will always be contained in the first part of the HISTORY keyword section; the presence of such a summary shall be indicated in the DAT-TYPE keyword discussed above. In the case where FITS data records accompany the header, USERS OF THE ARCHIVE ARE CAUTIONED THAT THE SUMMARY VALUES ARE ONLY MEANT TO DESCRIBE AND CHARACTERIZE THE DATA ... NOT TO REPLACE THEM. All summary lines follow the same general form: HISTORY SUBKEY ################ 'UNITS ' where the # field is a right justified floating point number. Format for Upper Limits: COMMENT *SUMMARY OF DATA - UPPER LIMIT HISTORY LIMIT 0.5 'JY/BEAM ' Upper limits in the Radio Science Network are always given as 3 standard deviation upper limits. Format for Spectral Lines: COMMENT *SUMMARY OF DATA - SPECTRAL LINE HISTORY LINEPEAK 0.5 'JY/BEAM ' HISTORY ERR-PEAK 0.1 'JY/BEAM ' HISTORY LINE-VEL 10.0 'M/SEC ' HISTORY ERR--VEL 200.2 'M/SEC ' HISTORY LINE-WID 2532.0 'M/SEC ' HISTORY ERR--WID 130.2 'M/SEC ' HISTORY LINEAREA 1243.1 'JY/B*M/S' HISTORY ERR-AREA 143.6 'JY/B*M/S' HISTORY LINEMEAN 32.1 'M/SEC ' HISTORY ERR-MEAN 10.2 'M/SEC ' The spectral line summary values LINEPEAK, LINE-VEL, and LINE-WID are determined from gaussian fits to the line profiles. If one or more parameters were fixed in a fit to the data, the assumed values are listed with no errors. Spectral lines with hyperfine structure (e.g., HCN) are fitted on the assumption that all hyperfine components have their nominal intensity ratios. Format for Continuum Observations: COMMENT *SUMMARY OF DATA - CONTINUUM HISTORY CONTFLUX 0.5 'JY/BEAM ' HISTORY ERR-FLUX 0.1 'JY/BEAM ' Format for Radar Observations: COMMENT *SUMMARY OF DATA - RADAR HISTORY XSECTION 30.0 'SQUARE KILOMETERS' HISTORY ERR-XSEC 6.0 'SQUARE KILOMETERS' 2.1.5.2 Observing window section Since many radio observations take place over several days, we include the precise observing windows in the HISTORY section according to the format: COMMENT *OBSERVING WINDOW SPECIFICATION HISTORY N-WINDOW # HISTORY WINDOW 'DD/MM/YY' ####### 'DD/MM/YY' ####### HISTORY WINDOW 'DD/MM/YY' ####### 'DD/MM/YY' ####### where N-WINDOW gives the total number of windows for observation and subsequent window lines give the date and time (in decimals as in TIME-OBS) of beginning and end of the observing window. The time fields are right justified floating point numbers. 2.1.5.3 Orbital elements section Radio observers track the comet "blind" and it is important to know the precise position on the sky that they were tracking. We include a provision in the HISTORY section to specify the two-body elements and observatory position data used to produce the topocentric ephemeris for tracking. COMMENT *ORBITAL ELEMENT SPECIFICATION HISTORY ORBELEM T - T if orbital elements are provided HISTORY LONGEAST 243.11046715 - east longitude of observatory (deg) HISTORY RHO--COS 0.8159113419 - radius*cos(lat) for observatory (units of Earth equatorial radius) HISTORY RHO--SIN 0.5765085118 - radius*sin(lat) for observatory (units of Earth equatorial radius) HISTORY ET-UT 53.18439 - Ephemeris Time - UT correction (s) HISTORY JD 2446471.16128 - Time of Perihelion passage (ET) HISTORY Q 0.5870959 - Perihelion Distance (AU) HISTORY E 0.9672671 - Eccentricity HISTORY SOMEGA 111.85336 - Arg. of Perihelion (deg) HISTORY LOMEGA 58.15313 - Long. of Ascending Node (deg) HISTORY I 162.23779 - Inclination (deg) 2.1.5.4 Antenna tracking section This HISTORY keyword specifies the antenna rms pointing errors. COMMENT *RMS POINTING ERROR OF TELESCOPE HISTORY POINTERR ################ 'UNITS ' 2.1.5.5 Calibration section This group of keywords provides information on details of the calibration process. COMMENT *CALIBRATION METHOD INFORMATION HISTORY CALMETH 'DESCRIPTION OF CAL METHOD' If the calibration method is unknown, then no line appears. Current possible values are 'CHOPPER WHEEL', 'NOISE TUBE', 'STANDARDS', 'ABSOLUTE'. COMMENT *CALIBRATION STANDARD INFORMATION HISTORY CALSRCE 'SOURCE NAME' ########## 'UNITS ' Source (or sources) used to provide principal calibration. The # field is a right justified floating point number. For planets as the calibrators, the assumed brightness temperature is given; otherwise, the calibrator flux density is given in Jansky. There may be more than one CALSRCE HISTORY line. COMMENT *SYSTEM TEMPERATURE ETC. HISTORY TSYSTEM ############### '_SB ' HISTORY TRCVR ############### '_SB ' Total system temperature (TSYSTEM) and noise temperature of the reciver alone (TRCVR). '_SB ' allows single side band measurement ('SSB ') or double sideband measurement ('DSB ') to be indicated. The # field is a right justified floating point number. HISTORY TAUZENTH ############### Atmospheric opacity at zenith. The # field is a right justified floating point number. 2.1.5.6 Observer's comment section This block of HISTORY lines contains any extra comments about conditions, data quality, etc. that are sent to the Discipline Specialist by the observer. There are generally fewer than eight such comment lines given. COMMENT *OBSERVER COMMENTS HISTORY OBSCOMM ROOM TO REPORT OBSERVER COMMENTS HISTORY OBSCOMM ... HISTORY OBSCOMM ... HISTORY OBSCOMM MORE ROOM FOR OBSERVER COMMENTS 2.1.5.7 Discipline Specialist's comment section Comments by the Discipline Specialist team on this observation. There are generally fewer than eight such comment lines given. COMMENT *DISCIPLINE SPECIALIST COMMENTS HISTORY DSCOMM ROOM TO REPORT DISCIPLINE SPECIALIST COMMENTS HISTORY DSCOMM ... HISTORY DSCOMM ... HISTORY DSCOMM MORE ROOM FOR DISCIPLINE SPECIALIST COMMENTS 2.1.6 Keyword block VI: Standard FITS keywords These keywords are used to describe the FITS data records. They are all standard and they are summarized in Table V. Table V. Keyword Block VI ______________________________________________________________________________ Keyword Type Description ______________________________________________________________________________ BSCALE R Scale factor data = tape * BSCALE + BZERO BZERO R Zero value BUNIT C Units of data 'JY/BEAM ' - for line and continuum data 'STANDARD DEVIATIONS' - for radar data BLANK I Value for out-of-range data CRVALn R Value of physical coordinate of nth axis at the reference pixel CRPIXn R Array location of reference pixel for nth axis CDELTn R Increment in physical coordinate along nth axis CTYPEn C Type of physical coordinate 'VELO-COM' - frequency coordinate for line work in m/s defined to be velocity relative to the comet 'VELO-GEO' - velocity defined relative to center of Earth 'FREQUENCY' - frequency offset of radar echo from expected value in units of Hz 'CIRCULAR POLARIZATION' - axis used to define different states of circular polarization: -1 = LHC; -2 = RHC 'LINEAR POLARIZATION' - axis used to define linear polarization position angle 'ECHO POLARIZATION' - axis used to define polarization of radar echo 'RAOFF ' - spatial coordinate for maps (deg) 'DECOFF ' - spatial coordinate for maps (deg) 'RA ' - coordinate used for drift scans (deg) 'MAP-TYPE' - coordinate to indicate type of drift scan map: 0 = map with comet in beam; 1,2 = maps of galactic background only CROTAn R Rotation angle of physical coordinate axis n ______________________________________________________________________________ 2.1.7 Keyword block VII: End statement This keyword is required by FITS to terminate the header: END 2.2 Types of Data in the P/Halley Archive. Several distinct types of data were obtained during the International Halley Watch, and each data type required the use of a slightly different type of FITS format. In this section, we review the individual data types and any special steps taken in formatting data of this type. 2.2.1 Upper limits As stated above in the description of the FITS format, upper limits are reported in the HISTORY section of the FITS header in the HISTORY LIMIT keyword. The detection status of a particular observation is summarized in the third character of the DAT-TYPE keyword. An S implies that the observation did not yield a detection and is reported as a limit. However, in some cases marginal results, designated by M in the DAT-TYPE keyword have also been reported as limits. 2.2.2 OH spectral line observations The principal type of data is the 18-cm OH observations. These data are archived in FITS format as one-dimensional spectra of the flux density of the comet as a function of the line of sight velocity. For most OH observations, the line of sight velocity is given with respect to the observer, although some observers transmitted their results to us in terms of the geocentric velocity. Many OH line observations were conducted using two receivers having orthogonal polarizations. In order to preserve this information, we have presented the polarized spectral data in a two dimensional format with a second axis to designate which polarization applies. These spectra will have the NAXIS keyword set equal to 2, and the second axis will be labeled either 'CIRCULAR POLARIZATION' or 'LINEAR POLARIZATION', as shown in Table V above. This method for designating polarization is similar to the convention used in many FITS formats, where a separate axis (often labeled 'STOKES') is used to give the full Stokes parameters of the data. However, full Stokes parameters have not measured in this archive, and so we have defined these new polarization axes to handle this situation. 2.2.3 Interferometric UV data Radio interferometers measure a source's visibility function, which is the Fourier transform of the source brightness distribution. In aperture synthesis imaging, a set of measurements of the visibility function are Fourier transformed to obtain an image of the source brightness distribution. Unfortunately, the processing steps required to make a map force the observer to specify many parameters that determine how the visibility data will be transformed to make the image. The specification of these parameters and the Fourieer transformation of the data, in our view, constitutes an interpretation of the data, and runs counter to the philosophy of a data archive. Thus, we have preserved the actual visibility data in this archive. The visibility data are presented in the extended FITS GROUP data format. This is the format currently used for visibility data by many of the world's interferometers, and FITS readers for visibility data should be able to read the files prepared for the IHW archive directly. We have tested the files in the data reduction program for the U.S. National Radio Astronomy Observatory (Astronomical Image Processing System = AIPS), and in fact the files are quite similar to the UVFITS format of AIPS. For spectral line data, AIPS cannot Fourier transform more than eight spectral line channels at a time. Therefore, following the style of the NRAO VLA, we have archived the 32 channel data that were typically obtained in 4 separate FITS files with 8 channels in each file. A fifth file usually accompanies this data and contains the broadband continuum data recorded at the same time as the spectral line data. 2.2.4 Radar data Radar observations of Halley's Comet were carried out only at the Arecibo Observatory during November 1985. We have recorded the average echo obtained during this experiment in a single FITS file. The radar observation is made by transmitting a single frequency tone in one circular polarization toward the comet and observing the echo in both polarizations. The echo is observed in spectral line mode, and a detection is sought at the correct Doppler shifted frequency given by the ephemeris of the comet. Thus, since this data type is identical in most respects to a spectral line observation, the data are recorded in a similar format. For a specular reflection, the echo is expected to be polarized in the sense opposite to that of the transmitted signal. However, real surfaces often contain significant power in the same sense as that trans- mitted, perhaps due to multiple reflections on the target. We have treated the echo polarization in the same manner as the orthogonal polarizations in the OH experiments, but with a special key to designate the "same" and the "opposite" senses of polarization. 2.2.5 Occultations Many occultation-type experiments were carried out during the Halley campaign. Unfortunately, relatively few were reported to the International Halley Watch for inclusion in this archive. The occultation data that are presented here employed the Milky Way itself as a background source and made observations of a track across the sky with and without the comet present in the beam. When carried out as a spectral line experiment, these data result in a two dimensional data type with spectra taken at many positions along a track on the sky. We have attempted to preserve the raw data here by saving these two dimensional images in the FITS file. Thus, a typical file contains: (1) the data with the comet in the beam; (2) one or more maps with the comet out of the beam, which were obtained on a different day. We have chosen to present these different maps as a three dimensional "cube" of data, with NAXIS = 3. The first axis is the frequency dimension of the spectra. The second axis is the position of the spectrum in RA. Finally, the third axis, labeled 'MAP-TYPE' defines which map is being presented. MAP-TYPE = 0 is the data with the comet in the beam, and MAP-TYPE not equal to 0 gives the map of the galactic background alone on one or more days of observation. Users are advised to check the individual FITS headers for further information on the definition of MAP-TYPE for specific dates of observation. 3. THE RADIO SCIENCE NETWORK INDEX TO THE CD-ROMS The IHW provides various indices to help users of the archive find the data that they want. For the Radio Science Network, there are two indices provided by the project which users will find useful: the quick look index and the printed archive (see Sec. 4 for a description), both of which contain information on all observations in the archive. The Radio Science Network provides a third, discipline specific, index which contains much more detailed information about the radio observations than the others. In selecting the information to be included in the Radio Science Index, we have attempted to include all relevant data from the FITS headers, within limitations imposed by standards set by the Halley Watch. The detailed format of the Radio Science index is given in Table VI. Table VI. IHW Radio Science Network Index Format ______________________________________________________________________________ Field Keyword Type Format Notes ______________________________________________________________________________ 1 OBJECT C A20 2 FILE-NUM N I6 3 DATE-OBS D A8 IHW Date Format 4 TIME-OBS N F6.3 5 LONG-OBS C A9 6 LAT-OBS C A9 7 SYSTEM C A8 8 OBSERVER C A24 9 COMMENT ADD. OBS. C A60 May exclude some observers 10 SUBMITTR C A24 11 SPEC-EVT L L1 12 DAT-FORM C A8 13 DIS-CODE C A12 14 DAT-TYPE C A6 15 OBSVTORY C A10 16 TELESCOP C A10 17 LOCATION C A30 18 INSTRUME C A20 19 CENTFREQ N F11.4 in MHz 20 BANDWIDT N F11.4 in MHz 21 BEAMSIZE N F6.4 22 BEAMELON N F6.3 23 BEAMROTA N F6.1 24 BEAMEFF N F6.3 25 EQUINOX N F8.3 26 RAOFF N F7.4 27 DECOFF N F7.4 28 MOLECULE C A10 29 TRANSITN C A20 30 RESTFREQ N F11.4 in MHz 31 RES-SPEC N F11.4 in kHz 32 HISTORY LIMIT N F11.4 in Jy/Beam 33 HISTORY LINEPEAK N F11.4 in Jy/Beam 34 HISTORY ERR-PEAK N F11.4 in Jy/Beam 35 HISTORY LINE-VEL N F11.4 in m/s 36 HISTORY ERR--VEL N F11.4 in m/s 37 HISTORY LINE-WID N F11.4 in m/s 38 HISTORY ERR--WID N F11.4 in m/s 39 HISTORY LINEAREA N F11.4 in Jy/Beam * m/s 40 HISTORY ERR-AREA N F11.4 in Jy/Beam * m/s 41 HISTORY LINEMEAN N F11.4 in m/s 42 HISTORY ERR-MEAN N F11.4 in m/s 43 HISTORY CONTFLUX N F11.4 in Jy/Beam 44 HISTORY ERR-FLUX N F11.4 in Jy/Beam 45 DATE-BEG D A8 Date Format 46 DATE-END D A8 Date Format 47 HISTORY NWINDOW N I2 48 HISTORY WINDOW (1) D A8 Start Date of 1st Window (Date Fmt) 49 HISTORY WINDOW (1) N F5.3 Start Time of 1st Window 50 HISTORY WINDOW (N) D A8 End Date of Last Window (Date Fmt) 51 HISTORY WINDOW (N) N F5.3 End Time of Last Window 52 HISTORY POINTERR N F10.2 in arcsec 53 HISTORY CALMETH C A20 54 HISTORY CALSRCE (1)C A15 Name of Cal Source 1 55 HISTORY CALSRCE (1)N F10.3 Value of Cal Source 1 56 HISTORY CALSRCE (1)C A15 Units of Cal Source 1 57 HISTORY CALSRCE (2)C A15 Name of Cal Source 2 58 HISTORY CALSRCE (2)N F10.3 Value of Cal Source 2 59 HISTORY CALSRCE (2)C A15 Units of Cal Source 2 60 HISTORY TSYSTEM N F7.1 Value Only 61 HISTORY TRCVR N F7.1 Value Only 62 HISTORY TAUZENTH N F4.2 63 BITPIX N I2 64 NAXIS N I2 65 BSCALE N F15.9 66 BZERO N F10.4 67 BUNIT C A15 68 BLANK N I6 69 DATAMAX N F10.4 70 DATAMIN N F10.4 71 NAXIS1 N I4 72 CDELT1 C A15 73 CRPIX1 C A15 74 CRVAL1 C A15 75 CTYPE1 C A25 76 NAXIS2 N I4 77 CDELT2 C A15 78 CRPIX2 C A15 79 CRVAL2 C A15 80 CTYPE2 C A25 81 NAXIS3 N I4 82 CDELT3 C A15 83 CRPIX3 C A15 84 CRVAL3 C A15 85 CTYPE3 C A25 86 NAXIS4 N I4 87 CDELT4 C A15 88 CRPIX4 C A15 89 CRVAL4 C A15 90 CTYPE4 C A25 91 NAXIS5 N I4 92 CDELT5 C A15 93 CRPIX5 C A15 94 CRVAL5 C A15 95 CTYPE5 C A25 96 NAXIS6 N I4 97 CDELT6 C A15 98 CRPIX6 C A15 99 CRVAL6 C A15 100 CTYPE6 C A25 101 PATH:VOLUME C A8 CD-ROM VOLUME NAME 102 PATH:YEAR SUBDIRECT C A5 YEAR SUBDIRECTORY 103 PATH:MON. SUBDIRECT C A3 MONTH SUBDIRECTORY 104 PATH:DAY SUBDIRECT C A3 DAY SUBDIRECTORY 105 PATH:HOUR SUBDIRECT C A3 HOUR SUBDIRECTORY 106 FILENAME C A8 FILENAME ______________________________________________________________________________ 4. THE RADIO SCIENCE NETWORK PRINTED ARCHIVE In addition to the FITS presentation of the Radio Science Network data, an additional format is available in the printed archive. This format provides most of the information that is necessary to make use of the data, as well as the "data summary" information included in the FITS headers, such as the line peak intensity and width for spectral line observations. The format of the printed archive for the Radio Science Network is shown below. 4.1 Printed Format I: OH Subnetwork and Spectral Line Subnetwork Since the OH Subnetwork and the Spectral Line Subnetwork contain the same data type, it is most economical to print both subnetworks together in the same subsection of the Radio Science part of the archive. Detailed description of this format is in Table VII. Table VII. Printed Format I ______________________________________________________________________________ Col. FITS Field Field Notes Keywords Format Header ______________________________________________________________________________ 1 DATE-OBS,TIME-OBS DD.TTTTT Date(UT) 10 FILE-NUM I6 RSN# 17 MOLECULE A5 Mol 23 DAT-TYPE (4th character) A1 DT Denotes Subnetwork 25 RESTFREQ (MHz) I6 Freq 32 RES-SPEC (kHz) I4 Res 37 HISTORY TSYSTEM (K) I5 Tsys 43 BEAMEFF (per cent) I2 BE 46 BEAMSIZE (arcsec) I4 HP 51 DIS-CODE (8th character) A1 BS Denotes beam shape 53 Radial Offset of I4 rho Beam from Nucleus (arcsec) 58 Position Angle of I3 PA Radial Offset (deg) For Limits: 62 A "<" symbol A1 63 HISTORY LIMIT (Jy/Beam) F6.1 Line Peak if value>10Jy/Beam or F6.3 if value<10Jy/Beam 80 A "-" symbol A1 Width 91 A "-" symbol A1 Velocity For Detections: 63 HISTORY LINEPEAK (Jy/Beam) F6.1 if value>10Jy/Beam or F6.3 if value<10Jy/Beam 69 A "plus or minus" symbol A1 Line Peak 70 HISTORY ERR-PEAK (Jy/Beam) F5.1 if value>10Jy/Beam or F5.3 if value<10Jy/Beam 76 HISTORY LINE-WID (km/sec) F4.2 80 A "plus or minus" symbol A1 Width 81 HISTORY ERR--WID (km/sec) F4. 86 HISTORY LINE-VEL (km/sec) F5.2 91 A "plus or minus" symbol A1 Velocity 92 HISTORY ERR--VEL (km/sec) F4.2 For All: 97 SYSTEM A8 System 106 OBSERVER A23 Observer 130 COMMENT NOTE A2 Note ______________________________________________________________________________ 4.2 Printed Format II: Continuum Subnetwork The data in the continuum subnetwork are fundamentally different from the spectral line data in the previous section. Thus they require anopther format, listed in Table VIII. Table VIII. Printed Format II ______________________________________________________________________________ Col. FITS Field Field Notes Keywords Format Header ______________________________________________________________________________ 1 DATE-OBS,TIME-OBS DD.TTTTT Date(UT) 11 FILE-NUM I6 RSN# 18 DAT-TYPE (4th character) A1 DT Denotes Subnetwork 20 CENTFREQ (MHz) I6 Freq 27 BANDWIDT (MHz) I4 Res 34 HISTORY TSYSTEM I5 Tsys 40 BEAMEFF (per cent) I2 BE 43 BEAMSIZE (arcsec) I4 HP 48 DIS-CODE (8th character) A1 BS Denotes Beam Shape 50 Radial Offset of I4 rho Beam from Nucleus (arcsec) 55 Position Angle of I3 PA Radial Offset (deg) For Limits: 60 A "<" Symbol A1 61 HISTORY LIMIT (Jy/Beam) F6.1 Flux Density if value>10Jy/Beam or F6.3 if value<10Jy/Beam For Detections: 61 HISTORY CONTFLUX (Jy/Beam) F6.1 if value>10Jy/Beam or F6.3 if value<10Jy/Beam 67 A "plus or minus" symbol A1 Flux Density 68 HISTORY ERR-FLUX (Jy/Beam) F5.1 if value>10Jy/Beam or F5.3 if value<10Jy/Beam For All: 75 SYSTEM A8 System 84 OBSERVER A30 Observer 116 COMMENT NOTE A2 Note ______________________________________________________________________________ 4.3 Printed Format III: Occultation Subnetwork Since the occultation data in this archive is of the same type as the OH and Spectral Line Subnetworks, they are presented in the same format. Detailed description is in Table IX. Table IX. Printed Format III ______________________________________________________________________________ Col. FITS Field Field Notes Keywords Format Header ______________________________________________________________________________ 1 DATE-OBS,TIME-OBS DD.TTTTT Date(UT) 10 FILE-NUM I6 RSN# 17 MOLECULE A5 Mol 23 DAT-TYPE (4th Character) A1 DT Denotes Subnetwork 25 RESTFREQ (MHz) I6 Freq 32 RES-SPEC (MHz) I4 Res 37 HISTORY TSYSTEM (K) I5 Tsys 43 BEAMEFF (per cent) I2 BE 46 BEAMSIZE (arcsec) I4 HP 51 DIS-CODE (8th Character) A1 BS Denotes Beam Shape 53 Radial Offset of I4 rho Beam from Nucleus (arcsec) 58 Position Angle of I3 PA Radial Offset (deg) For Limits: 62 A "<" symbol A1 63 HISTORY LIMIT (Jy/Beam) F6.1 Line Peak if value>10Jy/Beam or F6.3 if value<10Jy/Beam 80 A "-" symbol A1 Width 91 A "-" symbol A1 Velocity For Detections: 63 HISTORY LINEPEAK (Jy/Beam) F6.1 if value>10Jy/Beam or F6.3 if value<10Jy/Beam 69 A "plus or minus" symbol A1 Line Peak 70 HISTORY ERR-PEAK (Jy/Beam) F5.1 if value>10Jy/Beam or F5.3 if value<10Jy/Beam 76 HISTORY LINE-WID (km/sec) F4.2 80 A "plus or minus" symbol A1 Width 81 HISTORY ERR--WID (km/sec) F4.2 86 HISTORY LINE-VEL (km/sec) F5.2 91 A "plus or minus" symbol A1 Velocity 92 HISTORY ERR--VEL (km/sec) F4.2 For All: 97 SYSTEM A8 System 106 OBSERVER A23 Observer 130 COMMENT NOTE A2 Note ______________________________________________________________________________ 4.4 Printed Format IV: Radar Subnetwork There is only one radar observation in the archive, but for consistency we have made a printed format for it. The format follows the Continuum Subnetwork format and is described in Table X. Table X. Printed Format IV ______________________________________________________________________________ Col. FITS Field Field Notes Keywords Format Header ______________________________________________________________________________ 1 DATE-OBS,TIME-OBS DD.TTTTT Date(UT) 10 FILE-NUM I6 RSN# 18 DAT-TYPE (4th character) A1 DT Denotes Subnetwork 20 CENTFREQ (MHz) I6 Freq 27 BANDWIDT (MHz) I4 Res 34 HISTORY TSYSTEM I5 Tsys 40 BEAMEFF (per cent) I2 BE 43 BEAMSIZE (arcsec) I4 HP 48 DIS-CODE (8th character) A1 BS Denotes Beam Shape 50 Radial Offset of I4 rho Beam from Nucleus (arcsec) 55 Position Angle of I3 PA Radial Offset (deg) 61 HISTORY XSECTION F6.1 67 A "plus or minus" symbol A1 Cross Sect. In units of km**2 68 HISTORY ERR-XSEC F5.1 75 SYSTEM A8 System 84 OBSERVER A30 Observer 116 COMMENT NOTE A2 Note ______________________________________________________________________________ 5. UNITS IN THE RADIO SCIENCE ARCHIVE We have attempted to use a fixed set of standard units for the values given in the IHW archive. These units are given in Table XI. Where these units are not used, as in the printed archive, the index tables, or in certain values in the HISTORY section of the FITS headers, attention is explicitly called to the change of units. Table XI. IHW Radio Science Units _______________________________________ Angle Degrees Length Meters Time Seconds Frequency Hertz Velocity Meters/Second Flux Density Jansky/Beam* Radar Cross Section Square kilometers _______________________________________ * 1 Jansky = 1.0 x 10(-26) Watts per square meter per Hertz The adoption of the flux density unit, Jansky per beam, deserves some additional comment. This unit is well defined: the signal is described in terms of the flux density of a point source which would produce the same signal observed from the comet. The explicit use of "per beam" in the unit acknowledges that the coma is possibly resolved by the beam to an unknown extent. Some observatories, such as the VLA, have naturally already adopted this choice of units since they use celestial point sources to calibrate the instrument. All continuum observations also use Janskys to express their results regardless of how the data are actually internally calibrated. Thus, in both of these cases, the Jansky is the obvious choice of unit. For spectral line work on large single antennas, however, results are typically expressed in "antenna temperature" since they are calibrated by comparing the observed signal to a calibration signal of known noise temperature. In recent years, this unit has become rather confusing as a result of efforts to convert a relatively well defined observed quantity into a more physically meaningful unit which gives an approximation to the true brightness temperature of the source. Thus, various forms of "corrected" antenna temperature are in use at different observatories, and it is often not clear which corrections have been made to the data. We therefore favor a system in which the calibration is achieved by direct comparison of the cometary signal to celestial sources of known flux density, and the natural unit for such a comparison is the unit of flux density, the Jansky. Thus, all observations in the archive have been converted to these units using data provided by the observers. 6. CALIBRATION Although we have converted the data in the archive to a common unit of flux density, we have made no attempt to recalibrate data to a common flux density scale. The calibration scale for radio astronomy is well established at centimeter wavelengths, and in general, well known standard sources were used by the network observers. For wavelengths shorter than about 1 centimeter, however, the calibration becomes less precise as atmospheric attenuation becomes significant in the observations. In most cases, comparisons to celestial sources are more indirect and observers rely on absolute calibration schemes as their primary method. Ultimately, though, even these techniques use known sources, such as the planets, to calibrate the system, and we have attempted to archive information about these calibration sources with each observation. Calibration information that is supplied to us by the observer is given in the HISTORY section of the FITS header. The HISTORY CALMETH keyword provides an ASCII string with a brief description of the calibration method used. Three methods are commonly used: (1) STANDARDS indicates that the data were calibrated through direct comparison to standard sources; (2) NOISE TUBE indicates that the data were primarily calibrated by injecting power from a noise source into the receiver; (3) CHOPPER WHEEL indicates that the "chopper wheel" method was used; (4) ABSOLUTE calibration is used for the radar observations presented in this archive and is based on measurements of antenna and transmitter properties rather than on astronomical standards. This latter method uses the comparison of the noise power from an ambient temperature load to that produced by the sky emission to make an estimate of the optical depth of the atmosphere, and it is commonly used at millimeter wavelengths. Even in the cases of NOISE TUBE and CHOPPER WHEEL calibration, where celestial sources are not initially used to calibrate the data, the final calibration is generally made with celestial sources. Whenever a standard source is used for this purpose, its name and assumed flux density are given in the HISTORY CALSRCE keywords. More than one of these keywords may exist in the header if more than one calibration source is used. For planetary sources, the assumed brightness temperature is given rather than the flux density since planetary flux densities vary with distance to the object. Finally, the system temperature (defined to be the total system noise temperature including receiver noise and atmospheric and ground pickup) and the receiver temperature (defined to be the noise temperature of the receiver alone) are given in the HISTORY TSYSTEM and HISTORY TRCVR keywords; the atmospheric opacity at zenith is given in the HISTORY TAUZENTH keyword where appropriate. 7. THE OBSERVERS Many people have made substantial contributions to the success of the Radio Science Network of the International Halley Watch. First of all, we wish to thank the observers who have submitted data to the archive, since if it were not for their interest and assistance, there would be no archive at all. These observers are listed in Table XII. We also appreciate those who attempted to observe comet P/Halley even if they did not get useful data. In many cases, these early attempts paid off in our later studies of comet Halley. Table XII. IHW Radio Science Observers _____________________________________________________________________________ Observer Affiliation _____________________________________________________________________________ Abraham, Z. Instituto de Pesquisas Espaciais, Brazil Altenhoff, W. Max Planck Institut fur Radioastronomie, FRG Andersson, Ch. Onsala Space Observatory, Sweden Arnal, E. Instituto Argentino de Radioastronomia, Argentina Bajaja, E. Instituto Argentino de Radioastronomia, Argentina Batelaan, P. Jet Propulsion Laboratory, USA Batrla, W. University of Illinois, USA Baum, S. University of Maryland, USA Berulis, J. Lebedev Physical Institute, USSR Biggs, J. University of Sydney, Australia Bird, M. Universitat Bonn, FRG Bockelee-Morvan, D. Observatoire de Paris-Meudon, France Boriakoff, V. Cornell University, USA Botti, C. Instituto de Pesquisas Espaciais, Brazil Bourgeois, G. Observatoire de Paris-Meudon, France Bretas Filhd, F. Instituto de Pesquisas Espaciais, Brazil Butner, H. University of Texas, USA Bystrova, N. Special Astrophysical Observatory, USSR Campbell, D. National Astronomy and Ionosphere Center, Puerto Rico Cancoro, A. Instituto de Pesquisas Espaciais, Brazil Cersosimo, J. Instituto Argentino de Radioastronomia, Argentina Claussen, M. University of Massachusetts, USA Cohen, J. University of Manchester, UK Colom, P. Observatoire de Paris-Meudon, France Colomb, F. Instituto Argentino de Radioastronomia, Argentina Comoretto, G. Osservatorio Astrofisico Arcetri, Italy Cordes, J. Cornell University, USA Crovisier, J. Observatoire de Paris-Meudon, France de Pater, I. University of California, Berkeley, USA Del Ciampo, L. Instituto de Pesquisas Espaciais, Brazil Despois, D. Universite de Bordeaux, France Destombes, J. Universite de Lille, France Duncan, R. CSIRO Division of Radiophysics, Australia Ekelund, A. Onsala Space Observatory, Sweden Ekelund, L. Onsala Space Observatory, Sweden Encrenaz, P. Observatoire de Paris-Meudon, France Falchi, A. Osservatorio Astrofisico Arcetri, Italy Forster, R. CSIRO Division of Radiophysics, Australia Forveille, T. Universite de Grenoble, France Frerking, M. Jet Propulsion Laboratory, USA Friehe, K. Instituto de Pesquisas Espaciais, Brazil Gagliardi, L. Osservatorio Astrofisico Arcetri, Italy Galt, J. Dominion Radio Astrophysical Observatory, Canada Gaylard, M. Hartebeesthoek Radio Astronomy Observatory, South Africa Gerard, E. Observatoire de Paris-Meudon, France Gossachinskij, I. Special Astrophysical Observatory, USSR Gulkis, S. Jet Propulsion Laboratory, USA Harmon, J. National Astronomy and Ionosphere Center, Puerto Rico Haschick, A. Haystack Observatory, USA Hasegawa, T. Nobeyama Radio Observatory, Japan Hoban, S. University of Maryland, USA Huchtmeier, W. Max Planck Institut fur Radioastronomie, FRG Irvine, W. University of Massachusetts, USA Judaeva, N. Special Astrophysical Observatory, USSR Kaifu, N. Nobeyama Radio Observatory, Japan Kaufmann, P. Instituto de Pesquisas Espaciais, Brazil Kinzel, W. University of Massachusetts, USA Kitamura, Y. Nobeyama Radio Observatory, Japan Klein, M. Jet Propulsion Laboratory, USA Krevsa, E. Max Planck Institut fur Radioastronomie, FRG Kuiper, T. Jet Propulsion Laboratory, USA Lewis, M. National Astronomy and Ionosphere Center, Puerto Rico Losovski, B. Lebedev Physical Institute, USSR Madden, S. University of Massachusetts, USA Malzoni, M. Instituto de Pesquisas Espaciais, Brazil Martin, C. Instituto Argentino de Radioastronomia, Argentina Matthews, H. Hertzberg Institute of Astrophysics, Canada Mazzaro, R. Instituto Argentino de Radioastronomia, Argentina Melad, I. Instituto de Pesquisas Espaciais, Brazil Mirabel, I. University of Puerto Rico, Puerto Rico Montiero do Vale, J. Instituto de Pesquisas Espaciais, Brazil Morras, R. Instituto Argentino de Radioastronomia, Argentina Nelson, G. CSIRO Division of Radiophysics, Australia Norris, R. CSIRO Division of Radiophysics, Australia Ohishi, M. Nobeyama Radio Observatory, Japan Olalde, J. Instituto Argentino de Radioastronomia, Argentina Palagi, F. Osservatorio Astrofisico Arcetri, Italy Palmer, P. University of Chicago, USA Persson, G. Onsala Space Observatory, Sweden Petroni, M. Instituto de Pesquisas Espaciais, Brazil Pickett, H. Jet Propulsion Laboratory, USA Poppel, W. Instituto Argentino de Radioastronomia, Argentina Reynolds, J. University of Sydney, Australia Scalise, E. Instituto de Pesquisas Espaciais, Brazil Schaefer, M. Jet Propulsion Laboratory, USA Schloerb, P. University of Massachusetts, USA Schmidt, J. Max Planck Institut fur Radioastronomie, FRG Schraml, J. Max Planck Institut fur Radioastronomie, FRG Sestokas, B. Instituto de Pesquisas Espaciais, Brazil Shang, Q. Yunnan Observatory, People's Republic of China Shapiro, I. Harvard-Smithsonian Center for Astrophysics, USA Silva, A. Instituto Argentino de Radioastronomia, Argentina Snyder, L. University of Illinois, USA Sorochenko, R. Lebedev Physical Institute, USSR Stumpff, P. Max Planck Institut fur Radioastronomie, FRG Suzuki, H. Nobeyama Radio Observatory, Japan Swade, D. University of Massachusetts, USA Tateyama, C. Instituto de Pesquisas Espaciais, Brazil Terasranta, H. Helsinki University of Technology, Finland Terzian, Y. Cornell University, USA Thum, C. Institut de Radioastronomie Millimetrique, Spain Tofani, G. Osservatorio Astrofisico Arcetri, Italy Tolmachev, A. Lebedev Physical Institute, USSR Turner, B. National Radio Astronomy Observatory, USA Urpo, S. Helsinki University of Technology, Finland Vilas Boas, J. Instituto de Pesquisas Espaciais, Brazil von Kap-Herr, A. Max Planck Institut fur Radioastronomie, FRG Walmsley, M. Max Planck Institut fur Radioastronomie, FRG Wang, J. Yunnan Observatory, People's Republic of China Wannier, P. Jet Propulsion Laboratory, USA Webber, J. Haystack Observatory, USA Winnberg, A. Onsala Space Observatory, Sweden Wootten, A. National Radio Astronomy Observatory, USA Zimmermann, P. Universitat zu Koln, FRG Zinchenko, I. Lebedev Physical Institute, USSR _____________________________________________________________________________ 8. ACKNOWLEDGEMENTS F. P. Schloerb and W. M. Irvine, as leaders of the radio astronomy effort, have been aided in their effort by a number of students, post-docs and secretaries at the University of Massachusetts during the course of our involvement with the IHW. We gratefully acknowledge the efforts of R. Bassett, M. Claussen, C. Clemens, R. Molloy, G. Moriarty-Schieven, D. Swade, and L. Tacconi-Garman, who have provided assistance to the project at various times throughout its duration. As leaders of the Radio Science effort, Schloerb and Irvine would also like to acknowledge especially two of the other members of the Discipline Specialist Team listed in Table I. W. M. Kinzel, the manager of the Radio Science Archive, has made a substantial and noteworthy contribution of time and effort to the actual archiving of the data while serving as a graduate student at the University of Massachusetts. The archive that exists today would have been impossible to complete without his participation in the project. Finally, we would like to thank particularly our Co-Discipline Specialist E. Gerard for his continued leadership in the field of cometary radio astronomy, his enthusiastic support of the International Halley Watch, and his efforts on our behalf. F. Peter Schloerb and William M. Irvine Discipline Specialists for Radio Science Five College Radio Astronomy Observatory Department of Physics and Astronomy University of Massachusetts Amherst, MA 01003