Remote Sensing via Really Small
Satellites: Opportunities and
Challenges
Norman Fitz-Coy
ASTREC – Advanced Space Technologies
Research & Engineering Center, an NSF I/UCRC
Center for Remote Sensing
University of Florida
January 20, 2012
Annual Global Satellite Launches
Orbview-3 (last US Remote Sensing satellite)
Satellites Launched
140
120
100
80
60
RS
Other
40
20
0
Year
http://claudelafleur.qc.ca/Scfam-remotesensing.html
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Remote Sensing Satellites (2009-2011)
Year
Name
Classification
Country
Description
2009
PRISM
Nano (5kg)
Japan
Amateur/Student
2009
Razaksat
Mini (180kg)
Malaysia
Land man., resource develop
2009
Deimos 1
Micro (90kg)
Spain
Disaster Monitoring Constellation (DMC)
2009
Dubaisat-1
Mini (190kg)
Dubai
Optical (2.5m BW, 5m RGB)
2009
DMC-2
Micro (96kg)
UK
DMC
2009
Sumbandila
Micro (81kg)
SA
Ag. monitoring, disaster response,
2009
Oceansar-2
Big (960kg)
India
16th remote sensing
2010
Tandem-X
Big (1350kg)
Germany
Formation w/ TerraSAR-X
2010
Cartosat 2b
Big (694kg)
India
Optical (0.8m BW), resource man.
2010
Alsat 2A
Mini (116kg)
Algerian
Resource man, (Alsat 2B later)
2010
Tianhui 1
Chinese
3D mapping
2010
COSMO-Skymed 4
Italian
Civil/military reconn (4th in constellation)
2011
Resourcesat-2
India
Adv. resource man. (water, agri,…)
2011
Haiyang 2
China
Microwave radiometer, ocean map
2011
NigeriaSat 2
Mini (268kg)
Nigeria
DMC, urban planning, …
2011
Rasat
Micro (93kg)
Turkey
Multispectral imager,
Big (1206kg)
http://claudelafleur.qc.ca/Scfam-remotesensing.html
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Why Constellations?
 Improved temporal resolution
 Spatial distributed observations
RapidEye
COSMO-SkyMed
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Small Satellite SWaP Characteristics
Mini
(120 W)
Micro
(50 W)
“CubeSats”
Nano
500 kg
(20 W)
Pico
(2 W)
10 kg
100 kg
1kg
10
cm
SwampSat
(UF)
~30 cm
GeneSat
(NASA Ames)
~50 cm
UK-DMC2
CubeSat Constraints:
 Size, weight, and power (SWaP) limit ⇒ novel configurations/mission
 Budget (<<$1M per satellite) ⇒ COTS utilization
 Development Time ⇒ Less than 1～2 years development cycle
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~1 m
Nigeriasat-2)
CubeSats Launched
CubeSat Launches (2003-2011)
16
14
12
10
8
6
4
2
0
15
7
6
6
6
5
3
3
Year
SwampSat (2012): On-orbit validation of a 3-axis ACS capable of rapid
retargeting and precision pointing of CubeSats using control moment
gyroscopes (CMGs).
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CubeSats as Remote Sensing Platforms
“CubeSat” Paradigm
“BigSat” Paradigm
 Specialized capabilities
 Multiple copies with the same specialization
(redundancy)
 Global cross-strapping
 Individual systems less complex (less expensive)
 Launch campaign for constitution of constellation
 Duplication of each component
 Multiple cross-strapping
(redundancy)
 Complex system (expensive)
 Limited copies
 “Simpler” launch campaign
F1
...
F2
F1
F3
...
...
F4
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F1
F1
F2
F3
F1
F3
F3
F4
F4
F6
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...
...
...
F1
FA
F3
FB
F3
FA
F4
FB
F6
Fc
...
FA
FB
...
...
FA
FB
FC
F1
F1
F1
F1
F2
F2
F2
F2
F3
F3
F3
F3
F4
..
.
..F
.
4
F4
F4
Fn
Fn
..
.
Fn
Fn
..
.
Potential Launch Options
P-POD
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NLAS
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Ecliptic
Sample Mission
Disaster Monitoring Using Small Satellites
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Sample Mission
Disaster Monitoring: Provide imaging data with a temporal resolution
consistent with detection and monitoring
 Temporal resolution: hourly
 Spatial resolution: 10-25 m
 Constellation of LEO satellites
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Challenges: Orbit and/or Debris Mitigation
 9 satellites – 3 planes each with 3 satellites
 Constellation constitution/maintenance
 Meets 25 yr. orbital life requirement
 Safety of ISS (alt. ~400 km)
 Constellation below ISS
 Or ensure orbit altitude
maintenance
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Challenges: Resolution vs. Altitude
Resolution at Nadir (m)
2.50
2.00
1.50
D=0.1
D=0.25
1.00
D=0.6
D=1.2
0.50
0.00
100
200
300
400
500
Altitude (km)
600
rd
700
Pixel of ground element
Aperture of dia. D
R
Boresight
θ
η
Edge ray target
Image plane
f
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∆x
h
Challenges: Access Area
Instantaneous Access Area (IAA) – all area potentially visible by an
instrument or antenna
30.0
25.0
Access Area
λ (deg)
20.0
SSP
λmax
15.0
10.0
Footprint
5.0
0.0
100
200
300
400
500
Altitude (km)
600
Essentially nadir looking
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700
Challenges: Constellation Coverage
 R⊕ 

 R⊕ + h 
λmax
λMax = cos−1 
Sat spacing per plane
2π 2
=
S =
π
N 3
cos λstreet = cos λmax cos ( S 2 )
SSP1
Continuous Coverage
SSP2
SSP1
(Street of Coverage)
S < 2λmax
S
λmax
SSP2
SSP1
Limiting Continuous
Coverage
S = 2λmax
S
λmax
Intermittent Coverage
SSP2
SSP1
S
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Street of
coverage
(continuous
coverage)
S
λmax
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λstreet
SSP2
S > 2λmax
Conclusions
 Technical challenges







Attitude control (pointing accuracy ~ 10s of arcsec)
Electrical power (OAP ~10s of watts)
High bandwidth communication (data rate ~ 50 Mb/s)
Onboard computational power (distributed processing)
Deployable structures, thermal control (induces pointing disturbances )
Autonomous orbit control (drag compensation)
Dedicated launch opportunities
 Opportunities (launch, mission, …)

ELaNa – NASA’s Educational Launch of Nanosatellites
(http://www.nasa.gov/offices/education/centers/kennedy/technology/elana_feature.html)

NSF CubeSat based Space Weather and Atmospheric Research
(http://www.nsf.gov/pubs/2010/nsf10537/nsf10537.htm)

NASA OCT Franklin & Edison Small Sat Program
(http://www.nasa.gov/offices/oct/crosscutting_capability/index.html)



GENSO (Global Educational Network for Satellite Operations) – Network of
university and amateur radio ground stations (www.genso.org)
QB50 – Network of 50 CubeSats for in-situ measurements in the lower
thermosphere (https://www.qb50.eu/)
HumSat – Network of small satellites for humanitarian benefits
(www.humsat.org)
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