getdmdm [ parameter=value ... ] [ inputfile ... ]
Parameters are: entire message, update_ephem, max_dist, printout.
getdmdm outputs formatted Direct Mode Data Messages (DMDM) from DMDM TeraScan datasets that were produced by the DMSP ingest programs rtdin and rdsin. The DMDM is a text message that contains the orbital elements for the sending satellite along with other "special messages." These special messages can take one of eight forms that include information on orbital elements for other DMSP or NOAA satellite, changes in the OLS thermal/light fine schedule, launch dates of new satellites, etc (see dmdm).
The DMDM message is stored as a byte variable in the ".dmdm" datasets that are produced by the rtdin and rdsin ingest functions. Running with default parameter values, these two ingest programs will save 2048 characters (see parameter dmdm_len under rtdin and rdsin) of the transmitted DMDM telemetry, of which 184 characters make up the actual DMDM message and are continually repeated. getdmdm extracts the DMDM message by finding three consecutive, consistent 184-character patterns, and then decodes and formats the message for hardcopy or screen output.
Determines whether getdmdm will print the entire DMDM message in its raw encoded format or whether getdmdm will print out the DMDM message formatted, labelling all fields and messages contained within the DMDM (default). Answering yes to this question may be necessary if the telemetry is "noisy" and the formatting could not be completed because three consecutive patterns could not be found. The unformatted message, however, will only be useful if the user is able to decode the fragments of the DMDM message themselves (see dmdm).
Valid responses are [yes or no]. The default is no.
OPTIONAL. Determines whether or not to use the message-8 data to update the orbital elements.
Valid responses are [yes or no]. The default is no.
OPTIONAL. Used only if update_ephem=yes. Sets the maximum allowable distance between satellite position predicted by elements from DMDM and position predicted by existing ephemeris. Only existing ephemeric records within $ORBDATEDIFF days of the elements from DMDM are used in checking.
The default is 0, which disables any distance checking. A value in the range of 5-20 kilometers is recommended. It should be low enough to screen elements that would prevent data reception, but large enough to acount for orbital model differences between the 2-line DMDM elements and the 1-line elements used by TeraScan.
Determines whether the output is sent to the hardcopy device or the screen (default).
Valid responses are [yes or no]. The default is no.
The following example shows how to extract a formatted DMDM from the TeraScan dataset named f11.92345.0129.dmdm that was created in the EXAMPLES section of rtdin. The output shows the raw 184 character DMDM message first, followed by the orbital parameters for the f-11 satellite (the sending satellite), and two special message #5s, one for the DMSP F-11 satellite and one for the NOAA-12 satellite.
% getdmdm
input file(s) : char(75) ? f11.92345.0129.dmdm
entire_message : char( 3) ? [no]
printout : char( 3) ? [no]
DMDM Page 1
f11.92345.0129.dmdm Satellite f-11 Date 92/12/10 Time 01:29:33
-------------------- Raw DMDM Message --------------------
|**460922005937025225157826299 095428624862104527108136 23295|
|369246002052028521267 2316528919*563141187325333886400149868|
|4480437100*5461415561254839021001298954622452700. |
| |
------------------------------------------------------------
DMDM Orbital Elements For
Satellite Name : DMSP F-11
Vehicle Number : 22546
Object/NORAD Number : 21798
Ops Number : 46
Day of Month : 9
Ascending Node Descending Node Argument of
Crossing Crossing Perigee
Time Longitude Time Longitude
************* ****** ************* ****** ***
Current Ref. 09:22:00:59.3 70.25 22:51:57.8 262.99
Cur. Ref. + 7 09:54:28.6 248.62 10:45:27.1 81.36
Plus 24 hour 23:29:53.6 92.46 00:20:52.0 285.21 267
Plus 48 hour 23:16:52 89.19
*******************> Special Message 5 <*******************
DMDM Orbit Information Data For
Satellite Name : NOAA-12
Vehicle Number : 63
Object/NORAD Number : 21263
Ops Number : 63
Orbit Period : 1:41:18.73
Asc. Node Drift Rate: 25.33 (deg/rev)
Semi-Major Axis : 3886.4 (NM)
Eccentricity : 0.0014
Inclination : 98.68 (deg)
Apogee : 448.0 (NM)
Perigee : 437.1 (NM)
Constant Roll Angle : 0
*******************> Special Message 5 <*******************
DMDM Orbit Information Data For
Satellite Name : DMSP F-11
Vehicle Number : 22546
Object/NORAD Number : 21798
Ops Number : 46
Orbit Period : 1:41:55.61
Asc. Node Drift Rate: 25.48 (deg/rev)
Semi-Major Axis : 3902.1 (NM)
Eccentricity : 0.0012
Inclination : 98.95 (deg)
Apogee : 462.2 (NM)
Perigee : 452.7 (NM)
Constant Roll Angle : 0
-------------------- End DMDM Message --------------------
The `~' character appears in the DMDM message as a 'bad' character (i.e. if the telemetry was 'noisy' and the DMDM character could not be decoded, a '~' is put in its place).
For more information see the document called "32 appendix 50 - ICD-CWD-3004 DMDM interface control document", which has excerpts from the MARK IV Operations Instructions Manual #EX96M-2.1, or the document described as "3.15 PROGRAM DESCRIPTION - ODMLOD.PR."
Last Update: $Date: 1998/05/29 17:24:38 $