1 / 11

Orbit evolution, next steps

Orbit evolution, next steps. Tanja Zegers May 26st 2009. Historical overview. 11 Nov. 2007. 6 May 2004. OCM by increase of semi-major axis. Direct effect of OCMs is Resonance change Orbit period change eclipse duration On the long term this causes a shift in Solar elevation angle

axelle
Télécharger la présentation

Orbit evolution, next steps

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Orbit evolution, next steps Tanja Zegers May 26st 2009

  2. Historical overview 11 Nov. 2007 6 May 2004 • OCM by increase of semi-major axis. • Direct effect of OCMs is • Resonance change • Orbit period change • eclipse duration • On the long term this causes a shift in • Solar elevation angle • Latitude drift of pericenter • altitude of pericenter 11:3 25:7 18:5 11 Jan. 2009 2010 2004

  3. What has changed since January 2009 ? • Orbit files for analysis were delivered by FD, products (SPICE, MAPPS, DQC) available on ftp://ssols01.esac.esa.int/pub/data/ • (delayed by HP workload FD) • MEX extension perspective • 1. Science mission: ext. to end 2009, requested to end 2012 • => Maximize science output before 2012 • 2. Support and relay to ExoMars: launch 2016, operations 2017 • => Maximize durability of MEX to reach 2017/18

  4. Study cases, starting from current 25/7 orbit • In all cases Orbit Change 1st Jan. 1010 • Orbit and event files not fully validated by FD (time) • Orbit and general pattern (eclipses etc.) is fully representative, but details are not: • Ground track • Phobos • Ground track propagation was always to the east. • 7/2 has the cheaper ‘west’ version

  5. 25/7 continued to 2019 • 2012 – 2015 no SEA> 5 deg • After 2016 slightly higher SEA

  6. 5 Cases with increasing semi-major axis (max. 7/2E) EXM • SEA change in the period up to 2012: • < 10º • SEA change in period up to 2016: • 15-20º

  7. Pericenter altitude evolution • Apparently correlated to semi-major axis: • Lowest altitude in 25/7, highest altitude in 7/2E

  8. When OCM ? • Earliest Feb 2010 (after long eclipses) • MTP planning mid November 2009 • Orbit file generation 2 months • Decision on OCM mid September ExoMars LS mtp70 mtp71 mtp72 1 Feb. 2010 9 Oct ‘09 6 Dec ‘09 13 Aug. ‘09

  9. Analysis to be done in next months Fuel left Fuel used routinely (now 0.24 kg/yr) Eclipses, battery life ORBIT Change, resonance Solar elevation angle Surface coverage (EXM) Phobos ESOC Pericenter altitude PI-teams Occultations Seasonal/time of day Subsurface

  10. Schedule for next steps • Power analysis – next presentation • Science opportunity analysis • HRSC/OMEGA: effect on (global) imaging of SEA/lat and resonance/swath • MARSIS: effect on subsurface • Teams/MEXSGS: opportunities for atmospheric science, RSI (occultations), RSI gravity • Phobos opportunity analysis • FD – frequency of potential opportunities and cost of optimization • Fuel use in different cases (gravity anomaly effect) – FD • Decisions on MEX use as EXM support – TBD • Early September: Orbit working group meeting if needed to prepare for decision on orbit in mid-September (SOWG TBD)

  11. Fuel • Fuel • Needed for deltaV – 1 m/s = 0.125 kg fuel • Needed for orbit maintenance • 0.25 kg fuel per year for 18/5, higher for lower order resonance • Safe Modes (~ 0.25 per year) Propellant = fuel + oxidizer, oxidizer is over abundant on MEX, Fuel counts May 2009: 9 kg fuel left (worst cumulative case 0.9 kg left) If 4.5 kg fuel left => 9 years of operations (including Safe Mode, without OCM) Orbit change starting from 25/7

More Related