The CCSDS Orbit Data Messages – Blue Book Version 2: Status, Applica?ons, Issues David S. Berry / Jet Propulsion Laboratory, California Ins=tute of Technology, Pasadena, CA 91109 and David Finkleman / Center for Space Standards and Innovaon, Analy=cal Graphics, Inc., Colorado Springs, CO 80920 © 2010 California Ins=tute of Technology. Government sponsorship acknowledged. 1 The Need for Orbit Data Messages • The technical community requires essen=al elements of informaon about spacecra past, current, and future state of moon • For contact planning and execu=on • For satellite tracking, telemetry, and commanding • For maneuver development and collaborave operaons 2 Orbit Data Messages Were Developed to Meet Need • Work on the ODM standard commenced in the 1990’s • Became a CCSDS Blue Book in 09/2004 (“ODMV1”) • Incorporated Orbit Parameter and Orbit Ephemeris Messages • Orbit parameters for propagaon with astro models • Orbit ephemerides over a =me span for interpolaon • ISO TC20/SC13 and /SC14 commi\ed to collaborang on a modified ODM to accommodate newly iden=fied SC14 needs • Backward compability with standard two line element sets (TLE) • Inclusion of quan=fied uncertainty in orbits (covariances) • ODMV2 was formally published by CCSDS in 11/2009 • Orbit Parameter, Orbit Ephemeris, and Orbit Mean Element Messages with covariances 3 Introduc?on – Orbit Data Messages • Orbit Data Messages (ODM) is a CCSDS and ISO standard ("Blue Book") • Part of CCSDS Navigaon Working Group (WG) Technical Program • ODM was recently modified and updated • ODMs are consistent with modern Service Oriented Architectures • Messages are ASCII text in “Keyword Value Notaon” (KVN) format or Extensible Markup Language (XML) format • ODM sets standard format/content • Does not constrain the communicaon medium or transmission scheme • Does not require that data exchange partners operate in the same way or even use the same operaonal or astrodynamic tools • Simply a way to communicate essen=al spacecra orbit informaon clearly, completely, and effec=vely 4 Orbit Data Message Applica?ons • Space Situa?onal Awareness • Conjunc=on predic=on, es=maon, and response • Interoperable, effec=ve exchange of orbit data • Satellite Tracking, Telemetry, and Commanding • Interoperable satellite management and data extracton • Assured consistent units, reference frames, coordinate systems, =me references • Overcoming deficiencies in current de facto standards and prac?ces • Two Line Element sets lack essen=al elements of metadata and covariances • Enable high fidelity propagaon or interpolaon of exis=ng orbit parameter and orbit ephemeris messages 5 Significance of Covariances for Contact Management • Open loop poin=ng difficult w/o covariance info, complicang search • The satellite is likely to be somewhere within covariance ellipsoid but not necessarily on its mean orbit 6 Significance of Covariance for Collision Assessment • Figure shows mean locaons of two satellites and 3σ covariances • Satellites are most likely to be at the centers of the ellipsoids that describe the probability density of trajectory excursions • Satellites only 400 meters apart, but very unlikely to collide • Assessment based only on distance would generate a false alarm 7 OPM, OMM, OEM Content and Structure • ODMV2 Message Structure • Header, Metadata, & Comment features same for all messages • Header contains iden=ficaon informaon essen=al for parsing • Metadata (“data about data”) describes coordinate and reference frames, physical assump=ons, nature of mean or osculang element technique, and informaon essen=al to use the content • COMMENT feature for non-standard explanatory informaon • OPM Data Sec?on Overview • Required: Cartesian state vector at single epoch • Op=onal: osculang Keplerian elements; solar radiaon pressure,drag; maneuver parameters; covariance • OMM Data Sec?on Overview • Required: Mean Keplerian state at single epoch • Op=onal: TLE parameters; solar radiaon pressure, drag; covariance matrix • OEM Data Sec?on Overview • Required: Ephemerides relave to an epoch – posi=on, velocity • Op=onal: acceleraons to accommodate non-conservave forces, covariance matrix 8 ODMs Sa?sfy Requirements for a Variety of Missions Conjunction Maneuver Collaborative Station LEOP Situational Preflight Contact Warning Operations Keeping Awareness Planning Planning Header/Message Info Orbit Data Message Element Message Identifier for Parser x x x x x x x x Creation Date/Time x x x x x x x x Originator x x x x x x x x Metadata Spacecraft Name x x x x x x x x Spacecraft Identifier x x x x x x x x Ref frame origin (for lunar/interplanetary) x x x x x x x x Ref Frame/Coordinate System/Epoch x x x x x x x x Time System x x x x x x x x Data Epoch of Orit Data x x x x x x x Ephemerides (position, velocity) x x x x x x x Osculating Orbit Elements x x x x x x Spacecraft Parameters (Mass,Drag Area, Drag Coeff, Solar Rad Area, Solar Rad Coeff) x x x x x Position/Velocity Covariance (6x6) and Ref Frame x x x x x x Maneuver Parameters Ignition Epoch x x x Duration x x x Delta Mass x x x Maneuver Reference Frame x x x Delta V's x x x Conjunction Information Epoch of Conjunction x x x x Miss distance between osculating orbits x x x x Probability of Collision x x x x • Blue areas are essen=al metadata no maer what the applicaon • Orange areas are unique to specific missions, the depth of color emphasizing cri=cality. • Yellow areas indicate that only one of the elements of informaon is necessary • White areas are desirable or situaonal 9 Differences Between Orbit Data Messages V 1 & V2 • Orbit Mean-Elements Message (OMM) was added • 6x6 covariance matrix was added to all messages • Op=onal acceleraons were added to OEM state vectors • Julian Date formang op=on for =me fields was withdrawn • ODMV1 requirement to put object iden=fier in SPACEWARN format changed from a “shall” to a “should” • Maximum line width for all messages was increased to 254 • Text value fields restricted to all upper or all lower case • OPM spacecra parameters changed from obligatory to op=onal • User Defined Parameters feature was added to the OPM • Added op=onal keyword to specify reference frame epoch • Some restric=ons imposed on placement of comments 10 Mandatory Prototyping and Tes?ng • CCSDS requires “at least two independent and interoperable prototypes or implementaons must have been developed and demonstrated in an operaonally relevant environment, either real or simulated." • Nine tests of varying complexity were performed: • Simple OPM w/only a spacecra state • Keplerian elements • Maneuvers (impulsive and finite) • Covariance matrices • Interpolaon between states • Transformaon between formats • Where possible, test ar=facts were input to operaonal navigaon S/W used by the test conductors • Some tests involved exchange of new “user defined parameters” • Par=cipants: CNES, JAXA, NASA (GSFC &JPL), GMV, CSSI 11 ODMV2 Prototype Test Plan Test Spacecra Msg Type Agencies & Msg Flow Direc=on 1 SOHO OPM NASA/GSFC => NASA/JPL 2 SOHO OPM NASA/GSFC => NASA/JPL 3 SOHO OPM NASA/GSFC =>NASA/JPL 4 ISS/Zarya OMM CNES => CSSI => CNES 5 Iridium 33 debris OMM GMV => CSSI => GMV 6 SELENE OEM JAXA => NASA/JPL 7 MEX/ODY OEM ESA=>NASA/JPL,NASA/JPL=> ESA 8 SOHO OPM NASA/GSFC => NASA/JPL 9 ISS/Zarya OMM CNES => CSSI => CNES ’ CNES = Centre Naonal d Études Spaales JAXA = Japan Aerospace Exploraon Agency CSSI = Center for Space Standards & Innovaon GSFC = Goddard Spaceflight Center ESA = the European Space Agency JPL = Jet Propulsion Laboratory GMV = GMV 12 Guidance for Employing ODMs • Accelera?ons in the OEM Ephemeris • Fewer ephemeris points, and thus less disk space • Essen=al when drag and radiaon pressure, non-conservave forces are important • Not all navigaon S/W can process acceleraons as input • Interface Control Documents • Jointly developed Interface Control Documents (ICD) between exchange par=cipants should be nego=ated whenever possible • ODMs and their standard elements of data and metadata are essen=al for immediate interac=ons between operators who have not established ICDs • ODMs are guides for developing ICDs in due course • User Defined Parameters • Allow users to add mission-essen=al elements of informaon for which there is no other data exchange medium; use judiciously • OMM Conversion to TLEs • Programs conver=ng OMMs to TLEs must be aware of TLE rules (e.g., checksum, formang, angle precision, reference frame) • Covariances • Interpolang or propagang covariances requires great understanding and care 13 Agency/Opera?on Infusion There is no point in having a standard if no one uses it. • Organizaons currently using ODM: • ESA/ESOC • NASA/JPL • JAXA • Future and poten=al users: • ESA Space Surveillance Network • CNES • Satellite Data Associaon: Satellite Data Center • US Air Force Commercial and Foreign En==es (CFE) Program • Addi=onal NASA Centers • Organizaons and Suppliers with parsers and ability to ingest ODMs: • GMV • Analy=cal Graphics (Satellite Toolkit, Orbit Determinaon Toolkit) 14 Future XML Format • XML schemas that encode the ODM data items in progress • Target comple=on date of ODM XML version in late 2010/ early 2011 • Eliminates a number of excep=ons in the KVN formaed messages • Examples: • For the OPM and OMM, all header, metadata, and data lines must use KVN, however, in the OEM the ephemeris data line has a fixed structure containing seven required fields and three op=onal fields • OPM and OMM covariance matrices are expressed in KVN, while the OEM covariance matrix is WYSIWYG, easily recognizable as a 6x6 lower triangular matrix 15 Conclusion