4 Final Report - Emits - ESA
4 Final Report - Emits - ESA 4 Final Report - Emits - ESA
4 Final Report Alternative solutions which have been investigated are: • geostationary orbit with limited station keeping, • inclined geosynchronous orbit, • Molniya orbit (highly elliptical inclined orbit). The appealing features of these alternatives are on one hand potential propellant savings for station keeping and on the other hand improved viewing conditions over Europe. The maximum propellant saving may be achieved for a geostationary orbit with 7.5 deg inclination and 0 deg initial right angle of ascending node. This orbit is rather stable such that no orbit corrections are needed. However, as it is the case for all inclined geosynchronous orbits, the orbit trace projected onto the Earth surface is a figure of eight which the satellite passes through once per orbit. This yields that the satellite is half an orbit over Northern latitudes (with better viewing conditions over Europe) and the other half orbit it is over Southern latitudes. If no corrections of the orbital plane are performed, the local time of the equator crossing will change over the year. This means that the satellite is at the most Northern position e.g. at 12:00 at a certain day of the year but half a year later this position is achieved at midnight. Hence, the good viewing conditions at daytime are achieved for a certain part of the year only and become even worse for the other part of the year. Since this feature is a significant constraint for the mission flexibility, all alternatives with inclined orbits have currently been dropped. Orbit determination performance The achievable precision for the position of the spacecraft is important since it contributes to the overall pointing budget which is rather stringent. The preferred solution with the best performance is a ranging technique based on 2 or 3 ground stations and using a spread spectrum method for the ranging signal. The orbit determination accuracy is 100 m to 150 m (3σ) along track and 10 m to 20 m (3σ) across track. The interesting feature is that this technology shows the same performance right after a manoeuvre when using 3 ground stations. Moreover, this technique is routinely used by SES Astra which gives strong evidence that it can be successfully applied to Geo-Oculus. The following alternative technologies have also been investigated: • single ground station ranging + line of sight measurements, • dual ranging, • DARTS, • short baseline interferometry, • long baseline interferometry, • optical telescope, • use of landmarks, • GPS. The GPS option is currently being investigated for geostationary orbits. It may provide a similar nominal performance as the ground based spread spectrum method but a significant degradation is expected for a couple of hours after a manoeuvre. All performance data for above listed options are found in [RD 7]. Orbit transfer and launcher A geostationary transfer orbit strategy is suggested as baseline. The initial elliptical orbit provided by the launcher is changed to the final circular orbit with a liquid apogee engine installed in the spacecraft. The achievable maximum mass of the spacecraft in the final orbit is slightly higher Page 4-28 Doc. No: GOC-ASG-RP-002 Issue: 2 Astrium GmbH Date: 13.05.2009
4 Final Report compared to a strategy where the launcher provides a direct injection. Moreover, this strategy is a common standard with a high level experience whereas the direct injection is offered by few launchers only. Depending on the final launch mass of the spacecraft, the preferred launchers are Soyuz from Kourou (up to ~3 tons) and Ariane 5 (more than 3 tons). For alternatives of non-European launch service providers see next table. Table 4.2-1: Launcher Survey: Standard Launch into GTO including Performance Injection into GTO Launch European Perf. into ΔV to GSO Remark Service LSP GTO [m/s] Launcher Name Provider [kg] Ariane 5 ECA Arianespace Y 9000 1500 flight qualified Soyuz Fregat / Kourou Arianespace Y 3000 1480 under development Soyuz Fregat / Baikonur STARSEM Y 1840 1500 flight qualified Atlas 5 ILS N 8670 1804 flight qualified Delta 2 Boeing N 2120 1840 flight qualified Delta 4M Boeing N 6470 1800 not commercially available Delta 4H Boeing N 10819 1800 not commercially available Proton * ILS N 5530 1500 flight qualified Sea Launch Sea Launch N 5850 1500 flight qualified Land Launch * Sea Launch N 3600 1500 flight qualified for direct GEO GSLV Antrix N 2400 1650 flight qualified up to 2t H-2A MHI N 6000 1840 flight qualified up to 5t Long March 3B CGWIC N 5000 1840 flight qualified Falcon 9 Space X N 5070 TBD under development Angara 3 * ILS N 2400 1500 under development Angara 5 * ILS N 5400 1500 under development * performance for S/C + adapter; all other launchers are S/C separated masses 4.3 Payload 4.3.1 Imaging capability In order to support Fire Monitoring & Marine applications, the instrument provides simultaneous imaging of Earth scenes on four multi-spectral focal planes (UV-blue, Red-NIR, MWIR and TIR) with a ground FoV of 300x300 km (0.48x0.48 deg). The spectral channels are defined in the following figure together with the achieved ground resolution over Europe (worst case given at 52.5 °N corresponding to a viewing zenith angle of 60 deg). For some channels (e.g. for IR ones), subscript "a" refers to Fire Monitoring mission while "b" refers to Marine application and corresponds to different radiometric requirements (e.g. SNR & typical radiance). The VNIR resolution for marine applications is 80 m, twice that of other missions because pixel binning is necessary to meet the challenging SNR requirements of these applications (see next section). In addition, the Disaster Monitoring applications requires a VIS panchromatic (PAN) focal plane with higher resolution (10.5 m nadir, 21 m over Europe) and reduced FoV (157x157 km, i.e. 0.25x0.25 deg) imposed by the use of the same detector array as the UV-blue & Red-NIR channels. The PAN channel is separated in the field from the other channels. Doc. No: GOC-ASG-RP-002 Page 4-29 Issue: 2 Date: 13.05.2009 Astrium GmbH
- Page 1: Geo-Oculus: A Mission for Real-Time
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4 <strong>Final</strong><br />
<strong>Report</strong><br />
compared to a strategy where the launcher provides a direct injection. Moreover, this strategy is a<br />
common standard with a high level experience whereas the direct injection is offered by few launchers<br />
only.<br />
Depending on the final launch mass of the spacecraft, the preferred launchers are Soyuz from<br />
Kourou (up to ~3 tons) and Ariane 5 (more than 3 tons). For alternatives of non-European launch<br />
service providers see next table.<br />
Table 4.2-1: Launcher Survey: Standard Launch into GTO including Performance<br />
Injection into GTO Launch European Perf. into ΔV to GSO Remark<br />
Service LSP GTO [m/s]<br />
Launcher Name Provider<br />
[kg]<br />
Ariane 5 ECA Arianespace Y 9000 1500 flight qualified<br />
Soyuz Fregat / Kourou Arianespace Y 3000 1480 under development<br />
Soyuz Fregat / Baikonur STARSEM Y 1840 1500 flight qualified<br />
Atlas 5 ILS N 8670 1804 flight qualified<br />
Delta 2 Boeing N 2120 1840 flight qualified<br />
Delta 4M Boeing N 6470 1800 not commercially available<br />
Delta 4H Boeing N 10819 1800 not commercially available<br />
Proton * ILS N 5530 1500 flight qualified<br />
Sea Launch Sea Launch N 5850 1500 flight qualified<br />
Land Launch * Sea Launch N 3600 1500 flight qualified for direct GEO<br />
GSLV Antrix N 2400 1650 flight qualified up to 2t<br />
H-2A MHI N 6000 1840 flight qualified up to 5t<br />
Long March 3B CGWIC N 5000 1840 flight qualified<br />
Falcon 9 Space X N 5070 TBD under development<br />
Angara 3 * ILS N 2400 1500 under development<br />
Angara 5 * ILS N 5400 1500 under development<br />
* performance for S/C + adapter; all other launchers are S/C separated masses<br />
4.3 Payload<br />
4.3.1 Imaging capability<br />
In order to support Fire Monitoring & Marine applications, the instrument provides simultaneous<br />
imaging of Earth scenes on four multi-spectral focal planes (UV-blue, Red-NIR, MWIR and TIR) with a<br />
ground FoV of 300x300 km (0.48x0.48 deg). The spectral channels are defined in the following figure<br />
together with the achieved ground resolution over Europe (worst case given at 52.5 °N corresponding<br />
to a viewing zenith angle of 60 deg). For some channels (e.g. for IR ones), subscript "a" refers to Fire<br />
Monitoring mission while "b" refers to Marine application and corresponds to different radiometric<br />
requirements (e.g. SNR & typical radiance). The VNIR resolution for marine applications is 80 m, twice<br />
that of other missions because pixel binning is necessary to meet the challenging SNR requirements<br />
of these applications (see next section).<br />
In addition, the Disaster Monitoring applications requires a VIS panchromatic (PAN) focal plane with<br />
higher resolution (10.5 m nadir, 21 m over Europe) and reduced FoV (157x157 km, i.e. 0.25x0.25 deg)<br />
imposed by the use of the same detector array as the UV-blue & Red-NIR channels. The PAN channel<br />
is separated in the field from the other channels.<br />
Doc. No: GOC-ASG-RP-002 Page 4-29<br />
Issue: 2<br />
Date: 13.05.2009 Astrium GmbH
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