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 missionSWOT 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

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

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

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)

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 forthermal 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

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

Seasonal solar array efficiency Inclination 78 deg - altitude 950 km

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Seasonal solar array efficiency with constant tilt of 17 deg

Eclipse effect

Sun distance effect

Seasonal solar array efficiency with semi-fixed tilt between 0 and 90deg

Seasonal solar array efficiency with semi fixed tilt between 0 and 30deg

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?

07/07/2005

Altitude 813 km - site min 5deg

FAIRBANKS

WALLOPSFUCINO

SPITZBERG

Europe

-90

-60

-30

0

30

60

90

-180 -130 -80 -30 20 70 120 170

KaRIN data rate (without margin) : 256 Mbit/s (TBC)

Maximum downlink data rate in X : 620 Mbit/s only over ground stationsIt is impossible to downlink all data even with Ka band with these inputs

KaRIN data rate is the second key parameter

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

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, Trad=20°C, Téq=35°C without margin)

Without heat pipes With heat pipes

Lateral antiSun side – 1m² 280 W/m² 320 W/m²

Lateral Sun side – 1m² 0 W/m² 60 W/m²

2 velocity and anti-velocity side – 2m²

200 W/m² 260 W/m²

Earth side 0.5m² 140 W/m² 200 W/m²

Total 750 W max 1000 W max

Less stringent than power allocation

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