ESA's Biomass Mission System and Payload Overview
Arcioni, Marco; Bensi, Paolo; Fois, Franco; Gabriele, A.; Heliere, Florence; Lin, Chung-Chi; Massotti, L.; Scipal, Klaus
ESA, NETHERLANDS

Following a User Consultation Meeting on 5-6 March 2013 held in Graz, Austria, the Earth Science Advisory Committee (ESAC) has recommended to implement Biomass as the 7th Earth Explorer Mission within the frame of the Earth Observation Envelope Programme. Earth Explorers are the backbone of the science and research element of ESA's Living Planet Programme, providing an important contribution to the global endeavour of understanding Earth's System, particularly in view of global climate change.
This paper will give an overview of the satellite system and payload descriptions. The primary scientific objectives of the Biomass mission are to determine the distribution of aboveground biomass in the world forests and to measure annual changes in this stock over the period of the mission to greatly enhance our understanding of the land carbon cycle. To achieve these objectives, the Biomass space segment will consist of a P-band (435 MHz) Synthetic Aperture Radar (SAR) in side-looking geometry with full polarimetric and interferometric capabilities. The technical description of the Biomass mission is derived from the preparatory activities at Phase A level and it shows how candidate implementation concepts can respond to the scientific mission requirements. The system description is mainly based on the results of the work performed during parallel Phase A system studies by two industrial consortia (EADS Astrium Ltd., 2010; Thales Alenia Space Italy, 2010). Two implementation concepts are described, which provide viable options capable of meeting the mission requirements.
The Biomass space segment comprises a single low Earth orbit satellite platform carrying a fully polarimetric P-band SAR instrument. The SAR antenna is based on a large deployable reflector (12 m circular projected aperture) with an offset feed array.
The configuration of the satellite is strongly constrained by the accommodation of such very large reflector antenna inside the launcher. This large antenna must be folded for launch and deployed in orbit to form a stable aperture.
The Biomass mission will operate in a dawn-dusk, sun-synchronous orbit with a mean altitude of about 660 km and a local time of 6:00. The Biomass mission will last five years and comprises a tomographic phase followed by the nominal operational phase. The orbit is designed to enable repeat pass interferometric acquisitions throughout the missionís life and to minimise the impact of disturbances from the ionosphere. The baseline observation principle in the nominal phase is the double-baseline interferometric method with a repeat cycle of 17 days. In order to minimise the temporal decorrelation of the interferometric acquisitions, an optional observation concept with a repeat cycle as low as 3 or 4 days will be presented.
After an overview of the mission architecture and a description of the coverage strategy, the space segment is described followed by the launcher, the ground segment and operations concepts.

Bibliography
[1] European Space Agency (2012) Report for Mission Selection, ESA SP-1324(1), Mission Science Division, ESA-ESTEC, Noordwijk, The Netherlands, ISBN 978-92-9221-422-7, available at http://www.congrexprojects.com/13m09/selection-reports [2] European Space Agency (2006) The Changing Earth: New scientific challenges for ESAs Living Planet Programme. ESA SP1304, see also http://www.esa.int/esaLP