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ExoMars 2016 Mission TGO Aerobraking and Science Orbit ESWT #5 ESTEC, 14 September 2013. Daniele Temperanza , ExoMars GNC and AOCS System Engineer Michael Khan, Exomars Mission Analyst. TGO Aerobraking Timeline.
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ExoMars 2016 Mission TGO Aerobraking and Science OrbitESWT #5ESTEC, 14 September 2013 Daniele Temperanza, ExoMars GNC and AOCS System Engineer Michael Khan, ExomarsMission Analyst
TGO Aerobraking Timeline • Aerobraking reduces the orbit from a highly eccentric ellipse to a low near-circle, as required for science ops • Start of Aerobrakingearly Nov 16 • Solar Conjunction wait-out From apoares altitude of 7000 Km till SES angle >10̊ mid May-late Aug 17 • End of Aerobraking and start of Science Ops mid Nov 17 (including Commissioning) • End of Science Ops (after one Martian year) mid Oct 19
Aerobraking Orbit • Initial periares / apoares altitude 200/33474 Km • Final orbit altitude (near-circular) 400 Km • Orbit inclination (unchanged by aerobraking) 74 deg • Longest eclipse duration encountered 160 min
Aerobraking Main Control Parameters • Maximum peak heat flux 2800 W/sqm • Maximum heat load per pass 500 KJ/sqm • Maximum dynamic pressure 0.7 N/sqm • No Science Ops allowed • Aerobraking is a very critical phase and therefore only essential functions shall be supported
TGO Design and Autonomy during Aerobraking • Dedicated GNC mode to deal with atmospheric passes • HGA in stowed configuration during all Aerobraking • Solar Arrays and GNC contribute to the stabilization around the aerodynamic equilibrium point during the passes • Outside passes SA and S/C pointing are constrained to guarantee power and communication • Dedicated Aerobraking Safe mode • Acquire Sun pointing and perform automatic orbit maneuvers, then allow for communication to Ground Control for investigation and recovery
TGO Science Orbit • The baseline Science Orbit is a near-circular orbit with an altitude of ~ 400 Km (in line with the TGO Science AO), inclined at 74 deg with ground track that closes after 3-5 days (with gaps) • Perturbations introduce variation in eccentricity (up to 0.015) • The altitude over any given latitude may vary by +/- 50 Km around 400 Km during the course of one Martian year