by Marci Paskowitz Possner
Following Intelsats acquisition of PanAmSat in 2006, Intelsat desired to consolidate operations of both companies satellites using the Intelsat Flight Dynamics System (FDS). As part of the Intelsat integration project, GMV and Intelsat worked together to develop portions of the necessary software modules into FDS to support the flight dynamics operations of Boeing 702 satellites.
TaskIn its design of the modules for this custom software project, Intelsat and GMV sought to create a solution that would go above and beyond the original Boeing requirements by adding flexibility for users of the software. Specifically, the users are given as much control as possible in the computation of the maneuver plans and reconstruction.
GMV also planned to add the developed modules to focusSuite, the Companys Flight Dynamics Software. focusSuite is an advanced, off-the-shelf, multi-mission, multi-satellite flight dynamics solution for flight dynamics satellite control. The program provides a generic framework that allows further product development and evolution, including the ability to integrate external applications with ease. Productivity, system usability, accessibility and stability are dramatically boosted, thanks to an open framework, With an enhanced focusSuite, GMV would become one of only two suppliers capable of supporting Boeing 702 satellites.
ChallengesThe Boeing 702 satellite is one of the most complex geostationary (GEO) satellites, in terms of its flight dynamics system. The Boeing 702 uses the Xenon Ion Propulsion System (XIPS), which provides low-thrust propulsion. This means the satellite has a far different operations concept when compared to typical geostationary satellites using a chemical propellant. In particular, the station-keeping maneuver planning is unique as four maneuvers are executed every day.
These maneuvers are planned simultaneously for a 14-day cycle for a total of 56 maneuvers. The algorithms to be used for the maneuver planning are complex and quite different from those used for planning the maneuvers of typical GEO satellites, where maneuvers are performed only every two weeks. The maneuver reconstruction is also challenging as the maneuvers performed by the Boeing 702 can last as long as one hour. The telemetry values needed for the reconstruction will change throughout the maneuver. The technique used for many GEO satellite buses that use representative telemetry data for maneuver reconstruction were not sufficient for this project, as the Boeing 702 maneuver must be divided into segments with varying telemetry values considered for each segment.
Challenges also existed from a software engineering point of view. The goal was to create software modules that could be integrated into Intelsats Flight Dynamics System and GMVs focusSuite. Modules had to be designed that required no dependency on GMV or Intelsat libraries. In order to maintain consistency between the software modules and the rest of Intelsats FDS, it was crucial none of GMVs software libraries be incorporated into the development. Had Intelsat libraries been used, they would have been provided to GMV as black boxes, forcing a layer of integration and adding complexity to the software. Not using the Intelsat libraries had an additional benefit for GMV; it would ease the task of integrating the modules into focusSuite.
ImplementationThe algorithms used in the software modules were developed by GMV with support from Boeing and Intelsat. For the station-keeping maneuver planning, some studies were performed to determine how best to solve the maneuver planning challenges, such as an optimization problem used to determine how to distribute the four, daily maneuvers. GMVs solution resulted in maneuver plans consistent with those generated in operational reference data, while simultaneously minimizing the number of computations performed.
There was the added benefit of additional flexibility being integrated into the software. For the maneuver reconstruction, Intelsat users will have more control over how the telemetry data is interpreted as well as how the maneuver is divided into segments. The solution is quite flexible and does not dictate any particular maneuver division. In terms of the maneuver planning, users will have the capability of selecting elements of the maneuver plan that should be optimized, adding significantly more flexibility to the maneuver planning procedure.
ConclusionThe software modules were successfully developed by GMV with no dependence on Intelsat or GMV libraries and fulfilled all of Intelsats requirements. The end result was extensively tested against Boeing 702 operational reference data. Comparisons revealed the results obtained using GMVs software modules were equivalent to those in the reference data. GMV can now count itself as one of only two Flight Dynamics Software suppliers in support of the Boeing 702 satellite. The features and capabilities available in the software modules developed for Intelsat will also be available to users of GMVs focusSuite who also operate Boeing 702 satellites.
About the author
Marci Paskowitz Possner is a Lead Flight Dynamics Engineer at GMV Space Systems, Inc. She has worked as Project Engineer and Project Manager in the development of operational Flight Dynamics Systems for several low-earth orbit NASA missions (OCO, GLORY) and well as geostationary satellites (Intelsat 702s).