| Chris / Proba |
CHRIS/PROBA ACQUISITIONS
CHRIS (Compact High Resolution Imaging Spectrometer) is a physically compact payload as its name implies (weighing under 15 kg) and operates in the 'push-broom' mode. Its main applications will be in environmental monitoring, forestry inventory and precision farming.
From a 600 km orbit, CHRIS can image the Earth in a 14 km swath with a spatial resolution of 18 m (this is somewhat variable as the altitude varies around the orbit). Using PROBA's agile steering capabilities in along and across track directions enables observation of selectable targets well outside the nominal field of view of 1.3º. Images will generally be acquired in sets of 5, these being taken at along track angles of ± 55 degrees, ± 36 degrees, and as close to nadir as possible.
CHRIS operates over the visible/near infrared band from 400 nm to 1050
nm and can operate in 63 spectral bands at a spatial resolution of 36m,
or with 18 bands at full spatial resolution. Spectral sampling varies
from 2-3 nm at the blue end of the spectrum, to about 12 nm at 1050nm.
Sampling is about 7nm near the red edge (~690-740nm). The instrument is
very flexible and different sets of bands can be used for different applications.
Figure 2.1. Illustration of how CHRIS can hold a target in view by using PROBA's pitch control.
Key Characteristics:
| Spatial sampling interval |
18m on ground at nadir |
|---|---|
| Image area |
14 km X 14 km (748 X 748 pixels) |
| Number of images |
Nominal is 5 downloads at different view angles |
| Data per image(for a 14x14
km2) |
131 Mbits |
| Spectral range |
410nm to 1050 nm |
| Number of spectral bands |
19 bands at a spatial resolution of 18m 63 bands at a spatial resolution of 36m |
| Spectral resolution |
1.3 nm @ 410nm to 12 nm @ 1050nm (i.e it varies
across the spectrum) |
|
Programmable operation: |
|
| Across track pixel size |
18m or 36m |
| Along track pixel size |
finest resolution is 18m but can be made coarser
by changing the integration time |
| Spectral |
variable bandwidth and band location |
| Digitisation |
12 bits |
| Signal-to-noise ratio |
200 @ a target albedo of 0.2 |
Table 2.1. Key characteristics of CHRIS/PROBA.
-55° +55° -36° +36°
0°
Figure 2.2. The different five CHRIS-PROBA acquired images (16/07/04) overlaped to LANDSAT image (17/07/04) over the Barrax test site studied during SPARC-2004 campaign.
CHRIS-PROBA programmed acquisitions:
Table 2.2. CHRIS-PROBA acquisition programmed during the SEN2FLEX Mission 1 campaign
|
Date |
Time |
Satellite Zenith Angle |
Solar Zenith Angle |
|
29 May |
11:29 |
-20 |
19 |
|
5 June |
11:12 |
16 |
20 |
|
6 June |
11:24 |
-10 |
19 |
Table 2.3. CHRIS-PROBA acquisition programmed during the SEN2FLEX Mission 2 campaign.
| Date |
Time |
Satellite Zenith Angle |
Solar Zenith Angle |
| 10 July |
11:25 |
-17 |
|
| 17 July |
11:08 |
20 |
|
Figure 2.3. CHRIS/PROBA quicklook from the image acquired at 20/05/2005.