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