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Godspeed, LADEE! AGI software-based Flight Dynamics System to be tested on mission to Moon

By: Jim Woodburn

AGI software-based LADEE Flight Dynamics System from Analytical Graphics, Inc. on Vimeo.

NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is in the nose-cone of the Minotaur V rocket, awaiting launch from Wallops Flight Facility in Virginia tonight at 11:27 p.m. EDT. This mission marks many firsts—it's the first spacecraft built in-house at NASA's Ames Research Center in Moffett Field, Calif., without a prime contractor, the first launch of the U.S. Air Force's five-stage Minotaur V vehicle, managed and operated by Orbital Sciences Corp., the first lunar mission flown by Orbital and the first lunar mission launched out of Wallops. According to the NASA website, this approximately 160-day “robotic mission will orbit the Moon to gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky. Once launched, the spacecraft will enter into a series of phasing orbits that will allow it to approach the Moon from its leading edge, travel behind it and reemerge to execute a 3-minute Lunar Orbit Insertion maneuver that will place it in an elliptical retrograde equatorial orbit for 24 hours. A series of maneuvers will then be performed to reduce the orbit to nearly circular with a 156-mile altitude. After this, a 100-day Science Phase will commence, followed by a decommissioning period when the altitude will be lowered and the spacecraft will impact the lunar surface.” I am lucky to be on the East Coast for this launch as it will be visible to a large portion of the Eastern Seaboard (http://www.orbital.com/NewsInfo/MissionUpdates/MinotaurV/index.shtml). While it is past my normal bedtime, you can bet that I will be praying for clear weather and watching for LADEE to begin its journey to the Moon. The LADEE Flight Dynamics System (FDS) was built by our good friends at Applied Defense Solutions (ADS) and Space Exploration Engineering (SEE), in close coordination with Ames  where mission operations will be performed after launch. I was privileged to be part of the peer review team for the LADEE flight dynamics design and was very impressed by the exceptional quality of the people on the team. ADS has used AGI products to operate well more than 20 military, NASA and commercial spacecraft, including IBEX, LCROSS and the Radiation Belt Storm Probes, and the LADEE FDS is no different. The system is based on our STK, STK Astrogator and Orbit Determination Tool Kit software. Because the software has been proven in so many operational NASA missions and is in use at most centers, the LADEE team was confident in using it for their FDS. It also made collaboration that much easier. We spoke with John Carrico, senior scientist at ADS and part of the FDS team currently at Ames with SEE’s Mike Loucks, this week about the excitement surrounding the mission and the value of the STK-based FDS. “We factored in all of the orbit analyst decision points in advance, so the whole system is tailored for operational workflows,” John said. The user interface (UI) is available on multiple machines (up to 8 simultaneously with flexible licensing to add more as needed), and it allows users to configure it to run “automatically” or in an interactive mode. “They are not locked down to a hardcoded system,” John said. Users can kick off intensive analyses—a long orbit determination run or massive product generation—onto the server so that the desktops can remain in use. The LADEE FDS was built so that it can support multiple mission rehearsals and operations simultaneously, making it mission-independent. Also significant was the reuse of AGI products. Since the software has been employed for many other operational missions, including those in deep space, using it helped reduce technical risk and testing time. Here’s the breakdown of how AGI products are implemented for LADEE: STK and STK SatPro STK is used for all acquisition data and product generation—pointing products, constraints, eclipses, etc. It’s also used to plan all attitude maneuvers for the entire mission. “Every time the satellite does any pointing, all attitude and attitude rates are calculated by STK. That’s thousands upon thousands of quaternions throughout the mission,” John said. STK is also used to perform attitude constraint violation checks such as ensuring that the Sun does not enter the field of view of the star trackers. STK Astrogator Astrogator was initially developed by John when he worked here at AGI, so its no surprise how robust it is for space missions, especially in the areas of trajectory design and maneuver planning. In the case of LADEE, Astrogator was used to plan a series of maneuvers using a set of phasing orbits to target arrival at the Moon. It was also used to plan a series of “lunar orbit acquisition” maneuvers to get into orbit about the Moon, as well as maneuvers to lower LADEE’s orbit for science collection and to perform orbit stationkeeping. As a bonus, Astrogator was leveraged to provide unique capabilities for initial orbit determination (IOD), which brings us to … Orbit Determination Tool Kit Ahh, ODTK, my passion (along with quoting sophomoric films from the ‘80s). ODTK will be used to perform orbit determination for the entire mission, from launch and early operations to cislunar phasing loops to lunar orbit. I worked closely with John and the LADEE team to ensure that the lunar gravity field was modeled in a sufficient manner to meet requirements. I also personally supported the TAO (Trajectory, Attitude and Orbit) Team by generating synthetic tracking data to support operational readiness tests in preparation for launch. I have to commend the flight dynamics team on overcoming all of the obstacles I threw at them (even the unintentional ones). The LADEE FDS has been a true collaboration between ADS, SEE and NASA Ames and its contractors. Godspeed, LADEE!
Posted: 9/6/2013 9:18:11 PM


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