1. 07/07/2005 Coupling with PF2012: No existing PF “as is” able to accommodate Karin On going study in France to develop a new generation of PF product line to succeed Proteus, Myriade and Spot class. This PF product line cover micro satellite to large satellite based on the same avionics SWOT is one of the 8 reference potential mission for PF2012 Mission objective is to determine the spatial and temporal variability in freshwater stored in the world’s terrestrial water bodies + spatial altimetry over oceans. There is numerous secondary objective achievable such as ice cap and sea ice measurements. SWOT mission Main evolutions vs Water: Add ocean altimetry Orbit requirement based on a 78deg- 950km inclination orbit to avoid Tie Aliasing. Open trade-off on frequency for Nadir altimeter Open PF compatibility More data to transmit to ground

2. 07/07/2005 Agenda  Situation on Platform studies  Main key points studied for payload accommodation  Power versus “Drifting orbit + roll stability + fixed yaw” constraints  Data transmission to ground  Payload thermal control

3. 07/07/2005 Platform situation  No existing PF available after 2012 and compatible with SWOT constraints in Europe  On going activity in CNES to define a new generation of PF to succeed Myriade, Proteus and larger satellite: called PF2012  Concept with 3 nominal mechanical architecture to cover a large flight domain  Standardized avionic with power modularity such as on Telecom PF  High performances (>10years of life duration, pointing, DV capacity, data transmission…)  8 reference potential missions are based on this product line including SWOT mission

4. 07/07/2005 Power versus “Drifting orbit + roll stability + fixed yaw” constraints  SWOT need a « state of the art » stability in roll (few 0.1 arcsec over 10s)  Need a fixed solar array during measurements to avoid SADM perturbation  SWOT need a fixed yaw (antennas parallel to velocity vector)  Not compatible with yaw steering such as on Topex/Jason  SWOT need a drifting orbit to avoid tie aliasing  Sun elevation versus orbit plane varies from 0 to 90 deg  SWOT need a large payload power consumption  The sum of these constraints lead to a solar array efficiency over an orbit of 30% instead of 68% for a mission such as Jason.  The solar array surface shall be of 2m² per 100W of satellite power (with the most efficient existing solar cells: 3J AsGa and without margin)

5. 07/07/2005 Solar array proposed accommodation  Rotation axis around velocity vector  Fixed solar array with axis parallel to velocity  Tilt value constant at 17deg  Maximum “reasonable” SA surface 18 to 20m² (5 to 5.5kW BOL)  Yaw flip when Sun cross orbit plane to maintain a cold satellite side for thermal dissipation Velocity  Advantages of this accommodation  Maximize power with a fixed SA  Optimize inertia matrix  Minimize RF SA/PL interferences  Optimize payload thermal control  Minimize drag for POD Nadir Optimum if constant = 17deg

6. 07/07/2005 Power availability with Fixed (or semi-fixed) solar array  Perform a satellite YAW FLIP each time the SUN cross the orbit plane to maintain a cold side for thermal dissipation

7. 07/07/2005 Constraint on the payload power consumption versus orbit  There is no significant constraint on a 6h SSO orbit  In order to avoid a very specific satellite design, it is recommend to limit solar array surface at 20 m² in the case of a drifting orbit  allow 1000 W for satellite mean power  With an assumption of 300W for PF and 20% of system margin:  Allocation for payload mean power consumption is 560W including data storage, transmission consumption, and payload thermal control  If SSO orbit is definitely discarded, it is strongly recommend to limit payload mean power under 500W for phase 0 and phase A  A so large solar array need as a minimum a 2.38 internal diameter launcher fairing  Which US launch vehicle (s) shall be consider for studies?

8. 07/07/2005 KaRIN data rate (without margin) : 256 Mbit/s (TBC) Maximum downlink data rate in X : 620 Mbit/s only over ground stations It is impossible to downlink all data even with Ka band with these inputs KaRIN data rate is the second key parameter

9. 07/07/2005 Data transmission  Need to optimize transmitted data rate:  on board treatment (systematic or over limited zone)  mask on data over zone without water  With an objective of mean data rate of 30 (TBC) Mbit/s even if the peak rate reach 256 Mbit/s

10. 07/07/2005 Thermal control  The large power consumption of the payload need a large dissipation capability and order of magnitude for thermal dissipation are: ( Hypothesis:  =0.2 @10years,  =0.76, T rad =20°C, T éq =35°C without margin) Without heat pipesWith heat pipes Lateral antiSun side – 1m²280 W/m²320 W/m² Lateral Sun side – 1m²0 W/m²60 W/m² 2 velocity and anti-velocity side – 2m² 200 W/m²260 W/m² Earth side 0.5m²140 W/m²200 W/m² Total750 W max1000 W max Less stringent than power allocation

11. 07/07/2005 conclusion  SWOT is a reference potential mission for the new PF product line PF2012  The platform and satellite may be provided by NASA or CNES  Phase 0/A in CNES are performed on the basis of PF2012  No work are done for an accommodation on a US platform  The payload power consumption is the first key parameter (with a drifting orbit) to avoid a specific and expensive platform development, the solar array is fix during nominal operations.  The mean payload data rate is the second key parameter for the mission feasibility  The large size of solar panel will probably not be compatible with very small launch vehicle fairing  Need a dedicated launch (due to the specific orbit) with 2.38 m minimum fairing diameter