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Radar Astrometry Format

Astrometric observations made by radar are stored in two 80-column records. Columns marked as `blank' must contain spaces (ASCII 32).

The first record has the following format:

   Columns       Use
   1 - 12        Identical to columns 1-12 for optical
                   observations
  13             Blank
  14             Note
  15             "R"
  16 - 32        Identical to columns 16-32 for optical
                   observations
  33 - 47        Time delay (in µs), implicit decimal
                   point between columns 43 and 44
  48 - 62        Doppler shift (in Hz), with the sign always
                   in column 48 and an implicit decimal
                   point between columns 58 and 59
  63 - 68        Transmitter frequency (in MHz), implicit
                   decimal point between columns 67 and 68
  69 - 71        Observatory code for transmitter site
  72 - 77        Blank
  78 - 80        Observatory code for reception site
                   (often identical to columns 69-71)

The format of the second record is as follows:

   Columns       Use
   1 - 14        Identical to columns 1-12 of first record
  15             "r"
  16 - 32        Identical to columns 16-32 of first record
  33             "S" for surface-returned signals
                 "C" for signals from the (hypothetical)
                   center of mass
  34 - 47        Uncertainty on the time delay (in µs), implicit
                   decimal point between columns 43 and 44
  48 - 62        Uncertainty on Doppler shift (in Hz), implicit
                   decimal point between columns 58 and 59
  63 - 68        Continuation of transmitter frequency, if
                   necessary, blank otherwise
  69 - 80        Identical to columns 69-80 of first record
The time of observation is the time of reception of the returned signal and must be understood to refer to an integral second. For example, 1990 07 15.326389 corresponds exactly to 1990 July 15 07h 50m 00s UTC.


Example Observations

Below are some of the radar observations included in the Minor Planet Center's archives, originally taken from Ostro et al. (1991, Astron. J. 102, 1490):
                                    Column
         1         2         3         4         5         6         7         8
123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789

00433         R1975 01 22.187500  150885360    -         13     430 251 AJ102251
00433         r1975 01 22.187500S        15              20         251 AJ102251
01627         R1985 07 09.339583  202574571                    2380 251 AJ102251
01627         r1985 07 09.339583C        16                         251 AJ102251
     J90M00F  R1990 07 09.340278   33184859                    8495 253 AJ102253
     J90M00F  r1990 07 09.340278S         5                         253 AJ102253
0026P         R1982 05 26.928472               +     369692    2380 251 AJ102251
0026P         r1982 05 26.928472S                        05         251 AJ102251
    CJ83H010  R1983 05 11.916667               -    2213064    2380 251 AJ102251
    CJ83H010  r1983 05 11.916667S                        01         251 AJ102251


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