picture of the encyclopedia
previous next
Version 0.81 comes with a new web design! Please allow popups for navigation.

Spot 4


Designation 25260 / 98017A
Launch date 24 Mar 1998
Country of origin France
Mission Remote sensing
Perigee/Apogee 832 km
Inclination 98.7°
Period 101 min
Orbital cycle 3.7, 26 days
Launch vehicle Ariane V107

The total cost of the satellite over 6 years (contruction, launch, exploitation) is approx. $500 million

External resources


External resources

sat-index articles

Technical data


Prime contractor Matra Marconi Space
Platform Spot Mk 2
Mass at launch 2755 kg
Dry mass 2600 kg
Payload mass 1390 kg
Dimension 2.5 x 2.5 x 5.35 m
Solar array 4 x 8 m
Stabilization 3-axis
DC power EOL: 2200 W
Design lifetime 5 years

Telemetry: 1704 MHz
Telemetry: 2218 MHz (4096 kbps)
Telemetry: 8253 MHz
Command: 2042.408 MHz (2 kbps)
Command: 5690 MHz

2 HRVIR (High Resolution Visible IR) detectors

Wavebands 0.50-0.59 µm (green)
0.61-0.68 µm (red)
0.79-0.89 µm (near IR)
1.53-1.75 µm (mid-IR)
Swath width 60 km (each HRV)
Resolution Monospectral: 10 m
Multispectral: 20 m

CCD with 6000 points. Has the same on-board recorder as Helios 1A provided by Enertec (2 x 120 Gbits). HRVs are steerable to either side of the ground track (+/- 27°) to provide re-visits and stereoscopic images


Wavebands 0.43-0.47 µm (blue)
0.61-0.68 µm (red)
0.78-0.89 µm (near IR)
1.58-1.75 µm (mid-IR)
Swath width 2000 km
Resolution 1.15 to 1.7 km

Vegetation monitoring Instrument. Onboard storage: 2.25 Gbit

The PASTEL system (PAssager Spot de TElécommunication Laser) use the SILEX (Semiconductor Intersatellite Link Experiment) payload to downlink via Artemis at 50 mpbs. The link is operated at optical frequencies at a wavelength of 800 to 860 nanometers. The light source is a solid state laser diode operated typically at 60 mW optical power. The applied modulation scheme is direct intensity modulation. A photo diode is used as optical data detector.

The difficulty involves aligning and stabilizing two terminals which are on average 38 500 km away from each other, with a pointing error of less than 2 micro-radians. In other words, the beam from PASTEL (which at that distance, would have a diameter of 200 m) would have to be kept centred on OPALE with a tolerance of +/- 38m. This is equivalent to to hitting an orange with a rifle shot from 51 km!

© TBS Internet, all rights reserved. All reproduction, copy or mirroring prohibited. Legal notice
francais anglais contact