4 Final Report - Emits - ESA

4 Final
Report
• De-orbit ΔV: 10 m/s
• NSSK ΔV 400 m/s,
• EWSK ΔV 10 m/s
• Wheel off-loading + Rate Damping + Safe Mode = 15 kg (applicable to CPS only)
The main trade-off regarding the propulsion system is about the use of EPS:
• no EPS onboard (propulsion tasks entirely performed by CPS, all attitude control tasks
performed by reaction wheels)
• EPS only for reaction wheels downloading (GTO-GEO transfer and de-orbiting performed by
CPS, fine pointing manoeuvres for image acquisition performed by reaction wheels)
• EPS for attitude control (GTO-GEO transfer and de-orbiting performed by CPS, no reaction
wheels)
In this scenario, the results of the various propulsion system options are then to be analysed in a
trade-off analysis at system level, i.e. involving also AOCS and main satellite level design choices.
Therefore, the purpose of this section is just to prepare the input for such trade-off analysis.
In following sections, the mass budgets (main trade-off criteria) for the options in Table 4.5-12 are
derived from requirements and briefly analysed.
4.5.7.1 CPS
Geo-Oculus is a geostationary mission. Astrium has a long heritage of supplying geostationary
spacecraft, dating back to the 1970s. In addition to the telecom fleet there is a successful fleet of
scientific and earth observation missions including Mars Express which has achieved two years in
Mars Orbit, Venus Express currently in Venus orbit, and Rosetta and Cluster missions which are now
flying with bipropellant NTO / MMH propulsion systems. The combined experience of this wealth of
heritage shall enable Astrium to complete the study and return conclusions for the optimal CPS to
meet the Geo-Oculus mission requirements.
Astrium currently has 3 generic platforms for geostationary missions which can be considered for Geo-
Oculus. These are:
Eurostar 2000+
MON-3/MMH bipropellant propulsion system, an evolution of the Eurostar 2000 platform, featuring 4
propellant tanks, on a central cylinder supported structure
Eurostar 3000
MON-3/MMH bipropellant propulsion system, a larger version of the E2000+ platform. The design has
been expanded to include larger tanks to increase the mission capabilities of the design, featuring 4
propellant tanks on a central cylinder supported structure, in 4 sizes
Eurostar 3000C
The E3000C is an evolution of the E3000 design, based upon the successful Mars Express and Venus
Express spacecraft. It remains a MON-3/MMH bipropellant propulsion system, with heritage from
E3000 and Mars/Venus Express, but the platform is smaller than both E3000 and E2000+ to suit a
smaller payload requirement. It features 2 propellant tanks are (supported by a “single H” type
structure, demonstrated by the Mars/Venus Express spacecraft). As with Eurostar 3000, the tank size
is interchangeable.
Doc. No: GOC-ASG-RP-002 Page 4-67
Issue: 2
Date: 13.05.2009 Astrium GmbH