Practicing for Mercury
13 Apr 2010
(Source: Johns Hopkins Applied Physics Laboaratory)
It's not easy practicing for something no one has done before, but the MESSENGER team is giving it a go. Mission and science operators have wrapped up the third and fourth in a series of rehearsals for how the spacecraft will be operated once it is in orbit about Mercury.
"No spacecraft has orbited Mercury before; although the spacecraft has been operating since 2004 and has flown past Mercury three times, team members have no direct experience planning and scheduling daily science observations and data playback in such an environment," says Alice Berman, MESSENGER's payload operations manager at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "So we're working now, before we go into orbit, on a readiness plan to ensure that the mission's full science success criteria will be met."
That plan includes Week-in-the-Life tests (or "WITLs"), which simulate one or more weeks in orbital operations to test the new procedures and software being developed for the Mercury orbital mission.
"Once in orbit, we'll prepare and upload a new command load, containing merged instructions for the spacecraft and science instruments, once a week," says Berman. "It will take three weeks to prepare and validate each command load. Therefore, the science and mission operations teams will be working on multiple staggered command loads at any given time during the orbit year."
The first two WITL exercises - completed in 2009 - focused on new procedures and software. These built upon the lessons learned and improvements from the Day-in-the-Life tests that began in 2007. "One of the most critical new software tools is called SciBox, which plans the detailed science instrument activities for the entire orbital mission,"
Berman explains. "Most of the planning steps were practiced over an extended period to give teams enough time to learn the new process and software and train others on their teams." The initial exercises led to several software improvements.
This latest exercise focused on rehearsing the new process in a simulated timeframe typical of orbital operations. The Operations Team wanted to answer two questions: Can the planning process be accomplished in the defined timeframe? And can processes and procedures be further streamlined?
From January 25 to February 17, the team planned activities through SciBox, tested them to make sure they worked, and began implementing them while starting a new set of commands.
"The team clearly showed that it could perform the planning process within the given timeframe," Berman says, reporting back from the March 24 debriefing meeting. "Furthermore, the teams demonstrated the ability to meet the schedule despite the blizzards that closed the Lab for several days in February."
The remaining WITL tests will be completed in 2010. Exercises five through eight are planned to start this month, with four consecutive weeks being planned over a six-week period. This summer, additional exercises will be run to simulate contingency or anomaly situations that involve rework or replanning on a short schedule.
"By this fall, we plan to complete WITL exercises covering at least 10 different weeks and orbital conditions," Berman says. "It is critical to test the many different observing scenarios and orbital conditions the spacecraft will face when it orbits Mercury."
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as Principal Investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.