Flight Dynamics Officer
-t h e t r e n c h-
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- Anything that leaves the Orbiter gets the FDO’s attention!
- Upper Stage-assisted satellites (Inertial and Spin-stabilized)
- RMS-deployed spacecraft
- GAS can deployables or other “mini-ejectables”
- "Inadvertent" releases (i.e., EVA tools, non-stowable HST solar arrays, etc.)
- The FDO maintains an ephemeris of all deployed spacecraft for relative motion monitoring and for predicting tracking coverage in the post-deploy timeframe.
- Inertial Stages:
- Inertial Upper Stage (IUS)
- The CSTC (IUS - Sunnyvale) performs a Gamma-Guidance simulation and supplies the FDO with the deploy time.
- Transfer Orbit Stage (TOS)
- The TOS POCC (at KSC) performs a TOS guidance simulation and supplies the FDO with SRM TIG, from which the FDO computes the deploy time.
- In both cases, the FDO is responsible for state vector maintenance, transfer of specified trajectory information to the customer, and separation maneuver computations.
- The FDO will provide the Deploy and SEP PADs.
- Spin-stabilized stages:
- Payload Assist Module (PAM-D)
- Deployed with spin axis coincident with Orbiter -Z axis
- Syncom (or "frisbee"-type)
- Deployed with spin axis coincident with Orbiter +X axis
- The FDO is responsible for computing the deploy time and separation maneuvers.
- Typically, two sets of deploy computations are performed:
- The preliminary computations are made early in the deploy timeline and are reviewed by the customer.
- The final computations are made based on updated target information supplied by the customer to the FDO from the preliminary computations.
- RMS Deployables
- Typically, the deploy time is specified by some trajectory event such as orbital noon to allow proper crew viewing of the payload or by payload pointing, communication, or sunlight requirements.
- The FDO is responsible for computing deploy time, separation maneuvers, and, if applicable, station-keeping and rendezvous maneuvers.
- GAS-can ejectables or other “mini-satellites”
- The FDO computes deploy time and monitors post-deploy relative motion
- Inadvertent release… or “oops!”
- The FDO helps recommend best course of action for object retrieval or collision avoidance maneuver
- Post-deploy separation maneuvers are payload-specific, but can be grouped into three categories:
- Upper stage deploys:
- All upper stage deploys require a "final" separation maneuver that places the Orbiter "above and behind" the upper stage prior to SRM ignition.
- In addition, IUS and TOS deploys also require a "backaway" separation maneuver to insure adequate clearance prior to the final separation maneuver.
- The magnitude of the final separation maneuver is selected to protect for Orbiter tile erosion and payload explosion limits.
- RMS deploys:
- The typical separation provides a small backaway maneuver (0.5 to 1.0 FPS) followed by a 0.5-3.0 FPS in-plane maneuver.
- The exact separation profile will also depend on the payload requirements (e.g., whether the payload will be retrieved later, etc.).
- Generic Separation Maneuver (aka 1-2-3 SEP):
- Pg. 11-2 Orbit Ops Checklist contains the crew procedures.
- Sep sequence consists of a 1 FPS backaway maneuver followed 2 minutes later by a 2 FPS out-of-plane maneuver. A final 3 FPS posigrade maneuver is executed 15 minutes after the out-of-plane maneuver.