4 Final Report - Emits - ESA

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4 Final Report The achieved ground resolution & coverage are generally between threshold (T) and goal (G) requirements, with the following exceptions: • VNIR channels have a resolution (40 m & 80 m for marine) better than the G requirement • T requirement is not met in TIR for Fire Detection due to sensor size limitation. This is deemed acceptable because the MWIR band is actually used for fire area monitoring, whereas TIR bands are used to monitor fire temperature, for which resolution is not critical. Channel ID Center wavelength Bandwidth Focal planes (nm) (nm) UV1 318 10 UV2 350 10 VNIR1 412 10 VNIR2 443 10 UV-blue VNIR3 490 10 VNIR4 510 10 VNIR5 555 10 VNIR7 655 155 PAN VNIR6 620 10 VNIR8a 665 10 VNIR8b 665 10 VNIR9 681 8 VNIR10 709 10 VNIR11 VNIR12 753 779 8 15 Red-NIR VNIR13a 865 20 VNIR13b 865 20 VNIR14 885 10 VNIR15 900 10 VNIR16 1040 40 SWIR 1375 50 MWIRa 3700 390 SWIR MWIR MWIRb 3700 390 TIR1a 10850 900 TIR1b TIR2a 10850 12000 900 1000 TIR TIR2b 12000 1000 Mission Disaster Monitoring Fire Monitoring Marine Applications Figure 4.3-1: Spectral channels (optional channels are in blue) & imaging capability summary 4.3.2 Radiometric & image quality performances Ground Pixel Size at 52°N [m] Image ground coverage [square, km] T G T G Disaster monitoring 100 10 100 200 Fire monitoring 250 100 100 200 Marine applications 1000 100 100 500 Ground resolution & coverage requirements Channels Number of channels GSD (m) at 52.5°N FOV (km) PAN 1 21.0 157x157 UV-blue Red-NIR 4 8 40 40 300x300 Red-NIR 2 40 SW/MW IR 2 300 300x300 TIR 2 750 UV-blue 7 80 Red-NIR SW/MW IR 10 2 80 300 300x300 TIR 2 750 4.3.2.1 Disaster Monitoring The high resolution PAN channel drives telescope diameter (set to 1.5 m) & pointing stability requirements. The acquisition is performed in 4 successive images, all downloaded for on-ground processing for SNR & MTF recovery. Indeed, the Nyquist MTF requirement for the raw images is relaxed from 10% to 5% to allow best resolution. The required SNR is increased in the same ratio to keep constant the SNRxMTF figure of merit to account for SNR degradation in MTF recovery by ground processing. Thanks to that, a Ground Sampling Distance (GSD) as good as 10.5 m (nadir), i.e. 21 m at 52.5 N is achieved, close to Goal requirement (10 m) for Disaster Monitoring. This resolution is achieved with LoS pointing stability requirements of 5 µrad/s and 0.15 µrad p-p, well within the capability of the selected AOCS design based on magnetic reaction wheels. As shown in §4.4, selecting conventional ball bearing wheels mounted on isolators (jitter increased 0.25 µrad p-p) has however a modest impact, with nadir GSD degraded to 11.5 m (23 m at 52.5 N). The same CMOS detectors are used for all UV-VNIR focal planes to reduce development cost & risks. The GSD of the UV-blue & Red-NIR channels is then obtained from the PAN GSD in the ratio of the Page 4-30 Doc. No: GOC-ASG-RP-002 Issue: 2 Astrium GmbH Date: 13.05.2009
4 Final Report FoV (300/157 = 1.9), i.e. 20 m (nadir). Since no SNR requirements were derived from user needs, a value of 150 was selected for all VNIR channels, consistently with PAN channel and Sentinel 2 requirements (around 150 and up to 170 for some channels). The instrument parameters for each channel are summarised in Figure 4.3-2. The GSD at the maximum latitude where full performance is required is recalled in column 3.The MTF at Nyquist frequency in is given in column 4, showing that the 10% requirement is met for all multispectral channels. For the PAN channel, despite relaxation to 5%, the requirement is met without much margin. This clearly demonstrates that the maximum resolution achievable with a 1.5 m telescope is reached for this channel (10.5 m nadir). 1 2 3 4 5 6 7 8 9 Mission Channel GSD at 52°N (m) MTF at Nyquist Final SNR Nb of images Post Integration Integ. Time of image (s) Channel acq. time (s) Disaster VNIR2 40 0.117 150 1 No 0.009 0.088 Disaster VNIR3 40 0.116 150 1 No 0.011 0.088 Disaster VNIR4 40 0.115 150 1 No 0.014 0.088 Disaster VNIR5 40 0.111 150 1 No 0.017 0.088 Disaster VNIR6 40 0.110 150 1 No 0.021 0.088 Disaster VNIR7 21 0.051 300 4 No 0.013 0.352 Disaster VNIR10 40 0.111 150 1 No 0.029 0.088 Disaster VNIR11 40 0.115 150 1 No 0.005 0.088 Disaster VNIR12 40 0.112 150 1 No 0.034 0.088 Disaster VNIR13b 40 0.113 150 1 No 0.034 0.088 Disaster VNIR14 40 0.098 150 1 No 0.073 0.088 Disaster VNIR15 40 0.117 150 1 No 0.011 0.088 Disaster VNIR16 40 0.110 150 1 No 0.027 0.088 Figure 4.3-2: Performances for Disaster Monitoring The SNR obtained after accumulation of the number of successive images indicated in column 6 is given in column 5. All multi-spectral channels can be acquired in a single image, i.e. without postintegration, while keeping good image quality (MTF at Nyquist > 10%, see column 4). The integration time of individual raw images is given in column 8. The time to acquire the channel (last column) is obtained by multiplying the number of images by the largest value between the integration time and the array readout time. 4.3.2.2 Marine applications For marine applications with challenging SNR requirements, 2x2 pixel binning is used to increase the collected signal, so the final ground resolution is 40 m nadir and 80 m at 52.5°N, well within the goal requirement of 100 m. Thanks to this lower resolution, the requirements on the pointing stability during imaging periods can be relaxed to 10 µrad/s, allowing to largely reduce the tranquilisation time following a slew manoeuvre. For channels with high SNR requiring long exposure time, the image acquisition is split in several successive images to avoid pixel saturation & image smear due to pointing drift. These images are summed on-board, with for the most critical ones (UV-blue channels) compensation of the image motion (so-called "post-integration"). The instrument parameters for each channel are summarised in Figure 4.3-3. The MTF at Nyquist requirement (10%) is met with good margins for all channels. Post-integration with LoS motion compensation is only required for the bands of the UV-blue focal plane (UV1 to VNIR5). Other bands require several images to avoid saturation at typical flux, these images are simply added in the on- Doc. No: GOC-ASG-RP-002 Page 4-31 Issue: 2 Date: 13.05.2009 Astrium GmbH
Page 1: Geo-Oculus: A Mission for Real-Time
Page 7: DL Final Distribution List Report Q
Page 11 and 12: TOC Final Table of Content Report D
Page 13 and 14: 1 Final Report 1 Introduction 1.1 S
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