Predictions

The ILRS currently provides satellite predictions for the network in two formats: Tuned Inter-Range Vectors (TIRVs) and the newer Consolidated Prediction Format (CPF). This newer CPF format will be the operational format for prediction providers and network stations by June 30, 2006.

Tuned Inter-Range Vector (TIRV) is the ILRS standard for predictions, which are available via email (i.e., predictions exploder) or via anonymous ftp from the data centers (CDDIS, EDC) and/or the prediction centers. Daily TIRVs are also available via email. If you would like to be added to the predictions distribution list contact Carey Noll (carey.noll@nasa.gov).

For certain passive satellites, predictions can be generated months into the future, but the trend is to keep predictions fresh by generating them daily. This virtually eliminates the need for time bias and drag functions. The biggest challenge in predictions is generating accurate elements for the very low altitude missions (e.g., CHAMP, GFZ-1). A temporary ILRS working group, the Rapid LEO Predictions Team, has been formed to address this issue.

When SLR data for a given satellite is sparse, NORAD elements are sometimes used to compliment the SLR tracking data. For the microwave satellite (i.e., GLONASS and GPS), the satellite broadcast elements can also be used to generate the predictions.

Sometimes satellite maneuvers for the active satellites are required to keep the satellite in the desired orbit. For more information on maneuvers, read the ILRS maneuver notification procedure or access the index to satellite maneuver databases.

Consolidated Prediction Format (CPF) accurately predicts positions and ranges for a much wider variety of laser ranging targets than had been previously possible. Rather than using the "Tuned IRV's" with an integrator, the new predictions will provide daily tables of x,y, and z positions for each target that can be interpolated for very accurate predictions. CPF provides an expanded format capability and should greatly improve tracking on low satellites because the full modeling potential of the orbit computation at the prediction center will be passed on to the stations. Drag files and special maneuver files will no longer be necessary. These predictions are available via email (i.e., predictions exploder) or via anonymous ftp from the data centers (CDDIS, EDC) and/or the prediction centers. If you would like to be added to the predictions distribution list contact Carey Noll (carey.noll@nasa.gov).

When SLR tracking is not possible because of satellite anomalies (e.g., going into safe hold mode, etc.) the mission contacts are required to inform the stations of this abnormal situation by sending a short message to the URGENT email exploder. A follow-up message when the satellite returns to normal status should also be sent to the URGENT exploder. Mission contacts can provide more details about the satellite configuration and status directly to the stations using stations exploder.

Predictions

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