Orbit Analysis and Orbit Control Strategy for Sentinel-1 Mission

Paper number

IAC-08.C1.4.3

Author

Mr. carmelo carrascosa, GMV SA, Spain

Coauthor

Mr. Giacomo Taini, European Space Agency (ESA), Italy

Coauthor

Mr. Fernando Aleman, GMV S.A., Spain

Coauthor

Mr. Francisco J. Atapuerca, GMV S.A., Spain

Year

2008

Abstract

Sentinel-1 is a satellite system developed in the frame of the Global Monitoring for Environment and Security programme (GMES). Sentinel-1 is an imaging radar mission, aimed at providing continuity of crucial data for user services, initiated with ERS and Envisat satellites. Sentinel-1 is envisaged as a two-satellite system, each carrying a C-band Synthetic Aperture Radar (SAR), although the actual baseline takes into account a single satellite with the option of the second one.

TASI has been awarded by ESA for the development of this Sentinel-1 program. Sentinel-1 mission is nowadays under design phase B. The Sentinel-1 mission presents strong orbit maintenance requirements derived from the need of performing SAR interferometry in regular basis. The nominal frozen sun-synchronous orbit, having exact repeat cycle of 12 days, has to be kept during the entire mission lifetime within an orbital tube of 100-meters diameter (root mean square criteria), defined in Earth Fixed Frame. GMV and TASI have been collaborating in the orbit  analysis for Sentinel-1. This analysis includes the Reference Mission Orbit (RMO) definition, as well as of the characterisation of the orbit control strategy, trying to propose an acceptable solution from the point of view of operations without penalising the interferometric performances.

The definition of the RMO was the first step in the process of deriving the appropriated manoeuvre strategy that fulfils the maintenance requirement with the minimum delta-V budget. For the reference orbit definition, only the Earth gravity was taking into account. Trade-off among the most adequate Earth Geopotential model was performed. The orbit perturbations caused by the air drag and the third body (Sun and Moon) are the main contributors to make the orbit get out of the statistical tube. Their effects at different latitudes were analysed in order to provide the appropriated control strategy by means of combining in-plane and out-of-plane manoeuvres. To facilitate the ground operations, the control strategy has been defined in terms of ground track dead bands at different latitudes, even though the requirement is just referring to statistical values. Finally, the remaining orbit perturbations have been included in the model to determine the impact of these additional effects in the statistical definition of the orbital tube. In addition, other definitions of the RMO were evaluated with the purpose of reducing the total delta-V and/or the simplification of orbit maintenance manoeuvres. 

Abstract document

IAC-08.C1.4.3.pdf

Manuscript document

IAC-08.C1.4.2.pdf (🔒 authorized access only).

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