Challenge of Nano Satellite for Remote Sensing

Application

Akira IwasakiUniversity of Tokyo

Large Satellite Mission

TIR 8.125-11.65µm

whiskbroom 90m SWIR

1.6-2.43µm pushbroom

30m

VNIR 0.52-0.86µm pushbroom

15m

VNIR-stereo 0.78-0.86µm pushbroom

15m

Terra/ASTER(Advanced Spaceborne Thermal Emission and Reflection Radiometer)

A

B

C

Global Digital Elevation Model (DEM)http://www.ersdac.or.jp

Large Satellite MissionKaguya/LISM

(Lunar Imager Spectrometer)

Haruyama et al., Science 2008

Consistent geometry

ASTER/SWIR•Six bands in parallel•Time interval observation

Y-axisX-axis (flight direction)

Band 7Band 8Band 9Band 4Band 5

Band 6

Boresight

SpacecraftMajor Clock

1.024s

Band 6

SWIRSampling

Band 5

4.398 ms

356.238 ms

(a) Footprint (b) Timing

Consistent geometry

Line (pixel)(a) (b)

(c)

+1.0

+0.5

0.0

-0.5

-1.0

Line number

Reg

istra

tion

erro

r (pi

xel)

1 ar

csec

Relative displacementAbsolute displacementAttitude correction

-0.3

-0.2

-0.10

0.1

0.2

0.3

0 500 1000 1500 2000-0.3

-0.2

-0.10

0.1

0.2

0.3

0 500 1000 1500 2000

Teshima et al., IEEE TGRS 2008

BackgroundIncreasing Natural Disaster

•Earthquake•Tsunami•Volcano•Flood

Pakistan2004

Background

Frequent observation

10/26: (107, 88, 2) -5.724000degree

11/11: (107, 88, 2)-5.666000degree

10/17: (108, 88, 6)5.732000degree

08/30:(108, 88, 6)5.699000degree

09/15: (108, 88, 6)5.721000degree

07/22: (107, 88, 2)-5.699000degree

09/08: (107, 88, 2)-5.727000degree

Small satellite for RSAdvantage•Increasing observation frequency with inexpensive cost

Disadvantage•Pointing is not so stable as large satellite•Temperature is not controlled with high accuracy•Weight and size of mission instrument are limited

Technology developments for the first missionare dedicated to overcome above problems.

Development of Mission Instrument for First Satellite

with N. Miyamura, A. Enokuchi, N. Takeyama, Y. Nojiri, Y. Nakamura(UT, Genesia, Axelspace)

SpecificationScan Method Pushbroom Two dimensional

Exposure time 0.6 ms (for GSD 5m）

Scan time 2 s/scene 0.6 ms/scene

Pointing Stability

Requirement

Bellow 0.1deg/s in 0.6 msBellow 1arcsecin 2 s

Bellow 0.1deg/s in 0.6 ms

Data acquisition mode

Flying Direction

Two dimensional image acquisition

Size of scenes is 40 km X 40 km (TBD)Requirement for attitude stability is moderate.

Fundamental mode of observation is two dimensional.

Extended mode 1

Flying Direction

Crosstrack pointing scan

Swath is 4 times compared to normal scan.

Flexible selection of observation bands

Extended mode 2

Flying Direction Flying Direction

Pushbroom

Overlapped scan for DEM

Specific target is observed at two different angles.

Several observation mode is demonstrated on orbit.

Filter Spectrograph

Band1 Band2 Band3 Band4

LandSat/ETM+ Band1~Band4

Design wavelength of optics

450440 920900Wavelength (nm)

Flexible selection of observation bands is possible.

Focal Plane Design

Charge Coupled Device(CCD)

Image Circle~ 50 km

Detector Area

Users can request other types of focal planes.

Refractive optics is adopted.Robust to temperature change.

Signal to Noise Ratio

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80solar elevation [deg]

SNR

B G R NIR

Performance satisfies the requirement in spite of size of telescope.

LAUNCH

FY 2010 2011 2012

Schedule

MissionInstrument

Design

MissionInstrumentFabrication

GroundProcessingSoftware

MissionInstrument

Ground Test

SatelliteBus

Design

SatelliteBus Fabrication

& Software Development

MissionInstrument

Ground Test

Conclusion and Future VisionRS is the promising area for small satellites.

•Increase observation frequency

Technology innovations are needed for nano satellites.•Pointing accuracy, temperature stability, size•Data rate limitation

First satellite of the project is described.•GSD = 5-7 m, 4 bands, 50 km swath