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GSEOS::Case Studies

The MESSENGER mission  

GSEOS is used on all instruments on the MESSENGER mission and GSE Software is responsible for overall GSE and instrument integration. The setup chosen for MESSENGER was to enable all instrument visibility from one common configuration. This allows to switch between various instruments within one instance of GSEOS. Although this increases the overall data load on the system it turned out to be a convenient configuration for payload integration. Please take a look at the conference paper that was published at the 2003 RCSGSO conference in Pasadena, CA. 

The CASSINI/MIMI instrument  

On CASSINI we only used GSEOS for the MIMI instrument. In this scenario GSEOS is used also throughout all mission phases. The initial setup was I&T in the bench test configuration. Here we customized a driver for the Ballard Technologies MIL-1553 board for the use with GSEOS. The driver is a universal BIOS that allows to configure the bus timing with a simple configuration file. We tried to get a end-to-end test system, on CASSINI this involved the generation of SASF files and IEBs. SASF files allow the execution of instrument commands in a time tagged fashion and are a spacecraft wide scripting tool. GSEOS can read and execute SASF files as well as generate these files.

Generation of SASF files is done by point-and-clicking on the instrument commands which are laid out in a hierarchical GSEOS menu. Each invocation of an instrument command is logged to a log file with markup. A parser can read this marked up log file and generate the according SASF script. This script can then be run directly in GSEOS for testing purposes and delivered to JPL upon satisfactory execution.

Besides interfacing to the 1553 hardware in bench test configuration, the MIMI GSEOS can also communicate to the MOC servers. We can retrieve archived and realtime playback data. This allows us a very quick turn-around time to determine system functionality. The advantage of this setup is the familiarity of the user interface throughout all development and operation cycles. We recently also implemented alarm monitors that can notify users via email and pager.

Pluto New Horizons  

The New Horizons mission to Pluto has a similar setup to MESSENGER in that we support the entire mission with GSE services and integrate all instrument customizations within one configuration. This allows for a simple payload integration since all instruments can be tested side-by-side.

One interesting feature on New Horizons is the integration of telecommand (TC) and telemetry (TM) databases. In previous missions we always had to keep the TC and TM databases of the I&T system synchronized with the flight operations databases. This usually lead to an outdated GSE system since in later project stages the concern shifts away from the GSE. For New Horizons we have chosen a different approach. There is one master database for TC and TM (Excel spreadsheets). These spreadsheets can be converted into EPOCH (the ground operation system) format as well as into GSEOS configuration files. The emphasis on the conversion was a 'zero impact' solution such that instrument teams are not hesitant implementing a new TC or TM definition. This guarantees the GSE to be always up to date with the latest definitions.

Besides the tight TC/TM integration we also wanted to be able to execute STOL (Spacecraft Testing and Operations Language) scripts. These scripts are run during flight operations on the ground system.
We implemented a STOL interpreter that allows the instrument teams to execute their STOL scripts within the GSE. The ability to test actual STOL scripts early in the mission phase make a smooth system integration possible. EPOCH (the ground operation system) format as well as into GSEOS configuration files. A similar STOL interpreter was used on the MESSENGER mission and the 2003 RCSGSO publication cited in the MESSENGER case study gives more details about scope and implementation details.

Another aspect of the New Horizons mission is the MOC (Mission Operation Control) server integration. This setup is used in payload testing once the instrument is mounted on the spacecraft. Since the TC/TM definitions are automatically generated the only task left was the implementation of the MOC client together with and appropriate user interface to query archived data. Most MOCs implement their own protocol stack and therefore this part needs to be customized to fit the mission needs.


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