Spacecraft Observation File

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The SpacecraftObservationFile object provides functionalities for reading and writing SpacecraftObservation data (azimuth, elevation, range, range-rate, right ascension, and declination) to or from FreeFlyer's ASCII file format. The time system for data contained in the SpacecraftObservationFile is TAI in Modified Julian format and range and range-rate data are given in km and km/s, respectively. Azimuth, elevation, right ascension, and declination data are given in radians in the reference frame of the observing Sensor. Lastly, the spacecraft observer position is given in km, in the ICRF inertial reference frame.

 

For information on how to simulate Spacecraft Observation data, see Simulating Tracking Data.

For information on how to generate Spacecraft Observation files, see Generating Tracking Data Files.

For information on viewing and editing data in an Spacecraft Observation file, see Using the Tracking Data Editor.

For information on including an Spacecraft Observation file in a Kalman Filter, Unscented Kalman Filter, or Batch Least Squares OD process, see Including Tracking Data in an Estimation Process.

 

The Spacecraft Observation file format holds the observation epoch to the millisecond level.

 

An example of the format of a Spacecraft Observation file is given below. The columns from left to right include measurement data as follows:

 

Label

Units

Required

Description

Range

km

Yes

Range measurement.

Range Rate

km/s

Yes

Range rate measurement.

Azimuth/Right Ascension

rad

Yes

Azimuth or Right Ascension measurement (measurement type dictated by 'Angle Type').

Elevation/Declination

rad

Yes

Elevation or Declination measurement (measurement type dictated by 'Angle Type').

Epoch

days

Yes

Epoch of measurement, in the MJD TAI GSFC frame.

Observing Sensor ID

-

Yes

ID number of the observing sensor.

Observing Spacecraft ID

-

Yes

ID number of the observing spacecraft.

Observed Spacecraft ID

-

Yes

ID number of the observed spacecraft.

Angle Type

-

Yes

The type of angles measured (possible values: AzEl or RADEC).

Spacecraft Observer Position

km

No

The position of the observing spacecraft at time of observation, in the ICRF inertial frame.

Range validity flag

-

No

Flag indicating whether the Range measurement is valid.

Range Rate validity flag

-

No

Flag indicating whether the Range Rate measurement is valid.

Azimuth/Right Ascension validity flag

-

No

Flag indicating whether the Azimuth/Right Ascension measurement is valid.

Elevation/Declination validity flag

-

No

Flag indicating whether the Elevation/Declination measurement is valid.

 

Some example of observation file data:

 

Sample Observation File 1 (AzEl measurements)

12297.238457499    2.135224033   4.335511756   -0.616492305   25197.976087963   29   5   3   AzEl    1   1   1   1

13708.128070804    6.152020826   3.908099797   -0.326413058   25197.979560185   29   5   3   AzEl    1   1   1   1

15937.570221369    7.997769207   3.710554700    0.032234892   25197.983032407   29   5   3   AzEl    1   1   1   1

 

Sample Observation File 2 (RADEC measurements)

16905.226378790   -8.977009946   2.331375443    0.225204531   25198.014282407   29   5   3   RADEC   1   1   1   1

14158.547455177   -9.063519169   2.358530067   -0.039845580   25198.017754630   29   5   3   RADEC   1   1   1   1

11735.331555999   -7.072311621   2.226702991   -0.218066599   25198.021226852   29   5   3   RADEC   1   1   1   1

 

Sample Observation File 3 (AzEl measurements with Observer Position)

12297.238457499    2.135224033   4.335511756   -0.616492305   25197.976087963   29   5   3   AzEl -3410.6730  5950.9570 -1788.6270  1   1   1   1

13708.128070804    6.152020826   3.908099797   -0.326413058   25197.979560185   29   5   3   AzEl -2681.8432  5337.3893 -3815.8650  1   1   1   1

15937.570221369    7.997769207   3.710554700    0.032234892   25197.983032407   29   5   3   AzEl -1685.2488  4190.9361 -5461.2015  1   1   1   1

 

 

 

See Also


SpacecraftObservationFile Properties and Methods