RBar Approach RPO Sequence

The RBar Approach RPO sequence moves the chase satellite to approach or depart a target satellite along the RBar.

This sequence uses the following method. First, it performs a radial maneuver to initiate a radial rate toward or away from the target. It then performs small in-track maneuvers when either the in-track position or in-track rate errors exceed a threshold. These maneuvers keep the satellite within a small tolerance of being on the RBar during the approach.

An alternative to this sequence is to use an FMWaypoints RPO sequence with the initial state on the RBar and the final desired relative position also on the RBar.

This sequence does not allow the chase satellite to go through the zero-meter mark along the RBar. If it detects this condition, it will issue an error message and stop. Also, if the initial condition is not on the RBar, the sequence issues an error message and stops .

The following picture shows an approach from -1000 meters on the RBar to a final stopping RBar position of -50 meters in a transfer time of two hours.

Watch the following video to learn more about the RPO sequence on this page.

Sequence parameters

Option	Description
Final_Radial_Offset	Enter, in distance units, the stopping radial offset relative to the target.
Transfer_Time	Enter the duration of the RBar transfer time.
Max_InTrack_Error	Enter the maximum allowed in-track error.
Max_InTrackRate_Error	Enter the maximum allowed in-track rate error.
Engine_Name	Enter, as a string, the name of the finite maneuver engine model.
Maneuver_Type	Select the type of maneuver, "Impulsive" or "Finite," from the drop-down list.
WhoAmI	Enter, as a string, the name of the current satellite.
ThisSequence	Enter, as a string, the name of this sequence. This is nominally RBar_Approach, but if you insert the sequence multiple times in the MCS, Astrogator adds a monotonically increasing number to the end of the name (RBar_Approach1, RBar_Approach2, etc.).