e2v's CCD image sensor going onboard
Pleiades Earth observation satellite has outperformed
The e2v CCD (Charge Coupled Device) image sensors fitted
to the instrument of CNES (Centre National d'Etudes Spatiales)
Pleiades Earth observation satellite have delivered best
performance exceeding the original specification.
After environmental testing, the optical and radiometric
(image quality) performance of the image sensors was found
to have exceeded expectations, with the Instrument MTF (Modulation
Transfer Function) and signal to noise ratio 1.5 times better
than the original specification.
The 200kg, high-resolution instrument includes, for its
panchromatic focal plane, five e2v CCD98-50s, each with
6,000 pixels; therefore giving 30,000 pixels per line.
This CCD image sensor has following features:
A pixel size and pitch of 13µm square
Four phase parallel transfer electrode structure, implemented
in four levels of polysilicon
Longitudinal anti-blooming structures in every pixel, optimised
for back-illumination to maintain 100% fill factor
6,000 active pixels per line, with a maximum of 20 TDI lines
Selectable number of active TDI lines in flight
10 serial readout registers, each with an optimised output
amplifier, each output therefore serving 600 pixels per
line
Custom Aluminium Nitride package, with anti-reflective (AR)
coated window
The Pleiades satellite also includes a multispectral focal
plane, which utilises an e2v CCD sensor type AT71554, with
the following main features:
4 photosensitive lines
1,500 photosensitive elements per line
Pixel size 52 x 52 µm
PRNU (Photo Response Non Uniformity) 1% r.ms
Non-linearity: 1%
The Pleiades project is part of ORFEO (Optic and Radar Federated
Earth Observation system), a joint French-Italian initiative
by the countries' national space agencies CNES and Agenzia
Spaziale Italiana (ASI), marking a major technological advance
in optical Earth observation systems. The two Pleiades observation
satellites are scheduled for launch in early 2010 and 2011
respectively and will orbit the Earth, capturing very high
resolution panchromatic and multi-spectral images from an
altitude of 694km, for a period of at least five years.
Didier Dantes, Head of Imaging Chain Department, Thales
Alenia Space, Cannes says "The e2v CCD performance
for the Pleiades optical high-resolution imaging instruments
offers enhanced resolution of 70 cm over a wide swath (20
km), after fusion, between the visible and near infrared
bands."
Alain Bardoux, Head of Detection Chain Department from
CNES said "Thanks to the high photo response achieved
via the back-thinned technology, and the e2v sensors readout
rate of up to 66 MHz on 10 outputs, it is possible to meet
the signal to noise requirement with only 10 TDI lines selected,
without any satellite slowing."
Brian McAllister, General Manager of Space & Scientific
Imaging at e2v said "We worked very closely with Thales
and CNES to develop and produce these sensors. It is very
rewarding that the performance exceeds original specifications
and opens new possibilities for Earth observation applications."
For further details visit: www.e2v.com