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Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 1
Small Satellites for Earth ObservationProspects & Limitations
Rainer Sandau
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 2
OUTLINE
1. Why small satellites? 2. Small sat missions: Facts & Trends3. Application requirements4. Restrictions5. Future of small satellite missions6. Conclusions
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 3
1 M$ 10 M$ 100 M$
cost
1 yr 2 yrs 5 yrs
response time
examplesCubeSat: 1 kg, ca. 2 yrs, 0.2 M$
ENVISAT: 8 t, 15+ yrs, 3 × 109 $
mass
1 kg 10 kg 100 kg 10 000 kg
Pico Nano Micro Mini
Small Satellites Large Satellites
1000 kg
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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)
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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.
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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);
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 7
Earth Observation Request (1)
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9
100m 10m 1m 0,1m 0,01mgeometrischeAuflösung
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100m 10m 1m 0,1m 0,01mAuflösung
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GSD
Sp
ectr
al R
esol
uti
on
Pan
chro
mat
ic
Mu
ltis
pec
tral
Hyp
ersp
ectr
al - Hydrology
- Agriculture
- Ressource Monitoring
- Environmental Monitoring
- Forestry
- Intelligence Services
- Urban Development
- Topography
- Traffic
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 8
Earth Observation Request (2)
1
101
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105
1
1 year
10 years
1 10 100 1.000 10.000
Rev
isit
Tim
e [h
]
geometrische Auflösung [m]
1
5
- Kartographie
- Geologie
2
6
- Forstwirtschaft
- Ozeanographie
3
7
- Landwirtschaft
- Hydrologie
4
8
- Naturkatastrophen
- Meteorologie
1
2
3
5
6
48
7
1
101
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1 day
1 month
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10
1 10 100 1.000 10.000
ösung [m]
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105
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1
10
1 10 100 1.000 10.000
[m]
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- Mapping
- Geology
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- Forestry
- Oceanography
3
7
- Agriculture
- Hydrology
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- Disaster Monitoring
- Meteorology
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48
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GSD [m]
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 9
Optical Small Satellites
Ground Resolution Spectral Resolution Temporal Resolution
Increasing
Example: Eros-B/PIC-2Launch 25.04.2006Mass 350 kgGSD 0.82 m
Increasing
Example: Proba/CHRISLauch 22.10.2001Mass 149 kgHyperspectral Imager
Unique opportunity for affordableConstellation
Example: DMC-1Daily global coverageGSD 32 mSwath 600 km
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 10
Instrument & platform requirements
Optical P/L
High res imaging
GSD optics downlink
Stat. Dynam. construction Data rate & volume
MTFradiometry
MTFpointing
Massvolume
Antenna sizepower
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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)
N
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 12
Spatial Resolution
MTFSR = MTFOptics • MTFD • MTFLM • MTFJ
tint < 0.2 tdwell J < 0.1 x
MTFSR = MTFstatic/instrument • MTFdynamic/platform
sin ( )LM xc a k
sin ( )LM xc a k
2 2 2exp( 2 )J Jk
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 13
Spatial Resolution
0 0.5 10
0.5
1
Normierte Ortsfrequenz
MTFr1 i
MTFr2 i
MTFdi
f i
0 0.5 10
0.5
1
Normierte Ortsfrequenz
MTFa1 i
MTFs2 i
MTFr2 i
MTFdi
MTFpf i
MTFpf1i
f i
0 0.5 10.5
0
0.5
1
Normierte Ortsfrequenz
MTFdi
MTFs1 i
MTFs2 i
f i
MTFdi MTFa1
i MTFa2
i MTF1
i MTF2
i
0 0.5 1
0
0.5
1
Normierte Ortsfrequenz
MT
F v
on B
eweg
un
g u
m G
SD
x 0
.2, 1
, 1.5
1
0.30
MTFa1 i
MTFa2 i
MTFa3 i
10 f i
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
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 14
Pointing stability
From 600 km orbit, GSD = 1 m IFOV 1.7 rad 0.3 arcsec
Drift < 0.2 IFOV 2.4 mrad/s 8 arcmin/s
For TDI with N = 96 25 rad/s !
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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.
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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.
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 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
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 19
BIRD Payload Segment
Mass of s/c: 94 kg
Mass of p/l: 30.2 kg
WAOSS-B MWIR TIR Wavelength 600-670nm
840-900nm 3.4-4.2µm 8.5-9.3µm
Focal length 21.65mm 46.39mm 46.39 mm Detector CCD CdHgTe CdHgTe Ground pixel size 185m 370m 370m Ground sampling distance
185m 185m 185m
Swath width 533km 190km 190km 1 at 572km Orbit altitude
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 20
Fire detection by MODIS and BIRD (Australia, January 5, 2002)
MODIS: Fire map BIRD: Fire map
Earth from Space, 3rd Int. Conf., Dec. 4-7, 2007, Moscow, Russia > Dr. R. Sandau > 21
F = 1.2 x = 10 m
Nyquist frequency
optics
spatial frequency (cy/mm)