SMALL SATELLITES FOR AN OPERATIONAL AIR QUALITY SERVICE. Bryan de Goeij, Zeger de Groot, Jeroen Rotteveel, Nick van der Valk and Gerard Otter

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1 SMALL SATELLITES FOR AN OPERATIONAL AIR QUALITY SERVICE Bryan de Goeij, Zeger de Groot, Jeroen Rotteveel, Nick van der Valk and Gerard Otter

2 OUTLINE Introduction Mission definition Mission goal and requirements Constellation orbits Mission overview Satellite platform Instrument Conclusions

3 50 YEARS OF SPACE HERITAGE MORE THAN 40 YEARS OF FLIGHT HERITAGE WITH 100% RELIABILITY

4 INSTRUMENTS FOR MONITORING ATMOSPHERIC CHEMISTRY TROPOMI 2015 Sentinel 5P GOME / GOME ERS METOP 1, 2, 3 SCIAMACHY 2002 ENVISAT OMI 2004 EOS-AURA

5 A MICROSAT CHALLENGE Can we define a relevant air quality mission, based on: Our existing expertise regarding space borne spectrometers State-of-the-art microsat technology Here, relevant relates to both the data product(s), the measurement frequency, the global coverage, the cost and the development time

6 MISSION DEFINITION Measurement of tropospheric NO 2, with a spatial resolution of 1 x 1 km In a region of the Northern hemisphere, which covers most major cities, i.e. between 29 N (Houston, Cairo, Chongdu) and 56 N (Edinburgh, Moscow)

7 CONSTELLATION ORBITS We have considered two main constellations: 9 satellites in 3 sun-synchronous orbits (@ 600 km and ~98 inclination) 9 satellites in 3 lower inclination orbits (@ 600 km and 60 inclination)

8 CONSTELLATION ORBITS - 2 Number of daily accesses to a 56 Northern latitude location over a one year period for a 9-satellite SSO constellation with 9h00, 12h00 and 15h00 Local Time of the Ascending Node (LTAN)

9 CONSTELLATION ORBITS - 3 Number of daily accesses to a 56 Northern latitude location over a one year period for a 9-satellite constellation with 60 inclination orbit in three separate planes

10 CONSTELLATION ORBITS - 4 The 60 inclination constellation provides roughly twice the number of daily observations compared to the SSO constellation At 29 Northern latitude both constellations provided about 3 observations per day The local observation time of a 60 inclined orbit shifts roughly 20 minutes per day, which provides temporal sampling with a limited number of satellites

11 MISSION OVERVIEW Mission control Space Segment Ground Segment Groundstation Payload Data Ground Segment Launch Segment Space segment: 9 microsatellites Launch segment: 3 launchers 9 deployers Ground segment: communication mission control data processing and storage Small satellites for an operational air quality service 20 April 2015

12 SATELLITE PLATFORM The microsatellite is designed to fit in a Quadpack satellite deployer This provides a standardized interface with many different launch vehicles Moreover, multiple deployers can be fitted on a single launch vehicle Thus, several microsatellites can ride piggy-back with a primary payload

13 INSTRUMENT A compact imaging spectrometer: spectral range: nm spectral resolution: 0.5 nm spatial resolution: 0.1 field of view: 60 (full angle) Using free-form mirror technology, this performance is achieved with only 8 optical components Different wavelength regions can be selected, only by changing the grating

14 INSTRUMENT - 2 Compact design: fits in a volume of 10 x 20 x 20 cm 3 allows for two (!) instruments in a standardized 20 x 20 x 30 cm 3 satellite structure leaves sufficient room for supporting hardware

15 INSTRUMENT - 3 Structure is monolithic and contains all mirror mounting surfaces and the stray light baffles Structure is fabricated cost-effectively from aluminium, using investment (lost-wax) casting with 3D-printed moulds

16 FREEFORM MIRRORS Freeform (= anamorphic) mirrors aluminium + NiP plating diamond turning + computer controlled polishing freeform metrology: Nanomefos surface roughness: 0.5 nm RMS surface shape error: < 25 nm

17 SIMULATION EXPERIMENTS (OSSEs) Design A: spatial resolution 1 x 3 km Comparison in the Mediterranean area with ship tracks showing large bias between model and true state Design B: spatial resolution 2 x 6 km Larger coverage, due to wide swath, is beneficial over smaller pixel size

18 CONCLUSIONS We defined a relevant air quality microsatellite mission for a region of the Northern hemisphere, which covers most major cities Based on a compact, low cost imaging spectrometer: volume: < 10 x 20 x 20 cm 3 spectral range: nm (e.g. NO 2 ) spectral resolution: 0.5 nm spatial resolution: 0.1 field of view: 60 (full angle) The microsatellites fit in a standardized Quadpack deployer, ensuring many possibilities for an affordable secondary launch

19 THANK YOU FOR YOUR ATTENTION Len van der Wal,