Small Satellites for Earth Observation Prospects & Limitations Rainer Sandau

1. Small Satellites for Earth Observation Prospects & Limitations Rainer Sandau

2. OUTLINE • Why small satellites? • Small sat missions: Facts & Trends • Application requirements • Restrictions • Future of small satellite missions • Conclusions

3. Small Satellites Large Satellites CubeSat: 1 kg, ca. 2 yrs, 0.2 M$ examples ENVISAT: 8 t, 15+ yrs, 3 × 109 $ Pico Nano Micro Mini mass 1 kg 10 kg 100 kg 10 000 kg cost 1 M$ 10 M$ 100 M$ response time 1 yr 2 yrs 5 yrs 1000 kg

4. Why Small Satellites Classification parameters • Mass/Volume • Costs • Preparation time have large influence on • Launch costs • number of opportunities • adoption of new applications • temporal resolution (through constellations) • reliability/continuity (replacement)

5. The advantages of small satellite missions are: • more frequent mission opportunities and therefore faster return of science and for application data • larger variety of missions and therefore also greater diversification of potential users • more rapid expansion of the technical and/or scientific knowledge base • greater involvement of local and small industry.

6. Small satellite missions are supported by several contemporary trends: • Advances in electronic miniaturization and associated performance capability; • The recent appearance on the market of new small launchers (e.g. through the use of modified military missiles to launch small satellites); • The possibility of ‘independence’ in space (small satellites can provide an affordable way for many countries to achieve Earth Observation and/or defense capability, without relying on inputs from the major space-faring nations);

7. - Hydrology - Agriculture - Ressource Monitoring - Environmental Monitoring - Forestry - Intelligence Services - Urban Development - Topography - Traffic 1 1 2 2 3 3 4 4 1 1 5 5 6 6 2 2 7 7 8 8 9 9 5 5 6 6 4 4 Spectral Resolution Panchromatic Multispectral Hyperspectral 3 3 7 7 9 9 8 8 100 100 m m 10 10 m m 1 1 m m 0,1 0,1 m m 0,01 0,01 m m geometrische GSD Aufl Aufl ö ö sung sung Earth Observation Request (1)

8. 5 5 5 10 10 10 10 10 10 years 1 1 5 5 4 4 4 10 10 10 1 1 1 year 2 2 3 3 3 10 10 10 Revisit Time [h] 1 1 1 month 7 7 6 6 3 3 2 2 2 10 10 10 1 day 1 1 1 10 10 10 4 4 8 8 1 1 1 1 1 1 10 10 10 100 100 100 1.000 1.000 1.000 10.000 10.000 10.000 geometrische Aufl ö ö sung sung [m] [m] [m] GSD [m] - - Forestry Forstwirtschaft - - Kartographie Mapping - - Landwirtschaft Agriculture - - Naturkatastrophen Disaster Monitoring 2 2 1 1 3 3 4 4 - - Ozeanographie Oceanography - - Geology Geologie - - Hydrology Hydrologie - - Meteorology Meteorologie 6 6 5 5 7 7 8 8 Earth Observation Request (2)

9. Increasing Example: Eros-B/PIC-2 Launch 25.04.2006 Mass 350 kg GSD 0.82 m Unique opportunity for affordable Constellation Example: DMC-1 Daily global coverage GSD 32 m Swath 600 km Increasing Example: Proba/CHRIS Lauch 22.10.2001 Mass 149 kg Hyperspectral Imager

10. Instrument & platform requirements Optical P/L High res imaging GSD optics downlink Stat. Dynam. construction Data rate & volume Antenna size power Mass volume MTF radiometry MTF pointing

11. Radiometric aspects Example orbit: H=600km, vground 7km/s GSD = 10 m  tdwell 1.4 ms GSD = 1 m  tdwell 0.14 ms tdwell(1m)/tdwell(10m)=1/10 IFOV(1m)/IFOV(10m) = 1/100 For good signal and SNR • TDI with N stages  N • signal, • SNR (IKONOS, EROS-B) • Slow-down mode (EROS-A1)

12. Spatial Resolution MTFSR = MTFOptics • MTFD • MTFLM • MTFJ tint < 0.2 tdwell sJ < 0.1 x MTFSR = MTFstatic/instrument • MTFdynamic/platform

13. MTF: LM = 0.1, 1, 1.5 ∙ GSD MTF Detector, Jitter  = 0.1, 1 ∙ x MTF Detector, Sinus vibration a = 0.1, 1 ∙ x Total MTF with LM = 0.2 x,  = 0.1 x, a = 0.1 x, Detector-size x Spatial Resolution

14. Pointing stability From 600 km orbit, GSD = 1 m  IFOV  1.7 mrad  0.3 arcsec Drift < 0.2 IFOV  2.4 mrad/s  8 arcmin/s For TDI with N = 96  25 mrad/s !

15. Future of Small Sats for Remote Sensing • New capabilities • the convergence of data acquisition and data visualization technologies • the ready availability of new small launchers and the rise of “space tourism” • the development of smaller, lighter, lower power satellites that can act as a constellation or independently

16. Convergence of data acquisition and data visualization technologies Example: • NASA’s “A Train” (Aqua, CloudSat, CALIPSO, PARASOL, Aura, and OCO) + • NDVI small sat for crop yield forecasting in a particular region, Aerosol and cloud correction using data from the A Train.

17. Small launchers & „Space Tourism“ • Getting into space is still a challenge and costly • During the last 10 years more small launchers at prices reasonable compared to the cost of a small sat (e.g.NASA/DLR GRACE constellation with EUROCKOT, SS-19 ICBM) • New impetus of „space tourism“ (Oct.4th, 2004, Burt Rutan & Paul Allan win the AnsarX PRIZE) Looking back: At the turn of the last century, air travel was relatively risky and quite expensive. Now we fly e.g. apples half way around the world at prices that are competitive with local transport & production.

18. Conclusions • Developing Small Satellites for Remote Sensing is within the • means of many nations • They provide enormous opportunities : • To do more with less • Address local and global needs • Provides an affordable means to improve the temporal resolution • Focus the development of the technical infrastructure of a country • Reduce risk in the use of space

19. BIRD Payload Segment • Mass of s/c: 94 kg • Mass of p/l: 30.2 kg

20. Fire detection by MODIS and BIRD (Australia, January 5, 2002) MODIS: Fire map BIRD: Fire map

21. F = 1.2 x = 10 mm Nyquist frequency optics spatial frequency (cy/mm)