Techniques for simplifying operations using VML (Virtual Machine Language) sequencing on Mars Odyssey and the Space Infrared Telescope Facility
Christopher A. Grasso · NASA Technical Reports Server (NASA) · 2003
301-250D 303-64 1-5926 Abstract-VML (Virtual Machine Language) is an advanced procedural sequencing language which simplifies spacecraft operations, minimizes uplink product size, and allows autonomous operations aboard a mission without the development of autonomous flight software. VML is used on Mars Odyssey and Space Infrared Telescope Facility, and is slated for use on Mars Reconnaissance Orbiter. The language is a mission-independent, high level, human readable script. It features a rich set of data types (including integers, doubles, and strings), named functions, parameters to functions, IF and WHILE control structures, polymorphism, and on-the-fly creation of spacecraft commands from calculated values. The ground component of VML consists of a mission- independent compiler, a data-driven command generator, and an execution tool, all of which run under Unix. The compiler translates human readable source to a binary format. The data-driven command generator translates mission-specific spacecraft commands for the compiler from human-readble text to binary. The offline sequence execution tool runs sequences at speeds several thousand times real-time, and provides debugging features, integrated reports, and interactive execution options. These tools allow iterative development of sequences with a turnaround time of seconds rather than the hours or days typical with full-up lab testing. Parameterization and use of reusable functions called blocks onboard the spacecraft has several advantages over ground expanded sequences. Mission safety is enhanced, since blocks receive more scrutiny up front during development. Development of sequences is simplified, since blocks provide a rich set of behaviors that can be invoked. The review and test process for the invoking sequences is simplified, since the behavior of the blocks is well understood. Mission costs for autonomy are reduced, since responses to conditions are coded into blocks and upgraded without changing flight software. Uplink load is reduced, since the blocks physically reside onboard the spacecraft. VML use on Mars Odyssey and the Space Infrared Telescope Facility (SIRTF) has allowed spacecraft