Matra-Toulouse's SPOT 4 uses a Spot Mk 2 bus. By the time of launch in 1998, SPOT 4 was eagerly awaited, after 18 months dependence on the aging SPOT 1 and 2 following the SPOT 3 failure. SPOT 4 introduced a new IR band and a vegetation instrument. The SILEX experiment would test optical comms with Artemis.
Mass is 2755 kg launch, 2600 kg dry. Size is 2.5 x 2.5 x 5.6m, with a 4 x 8 m solar array.
The vegetation instrument has the same bands as HRVIR, but with a 2250 km swath. The DORIS system determines the position of the satellite to 10 cm with Doppler techniques. ESBT is an S-band transponder for SPOT 4 command and control via Artemis. PASTEL (Passager SPOT de Telecommunication Laser) is part of the SILEX experiment, with high speed image transmission via laser link with Artemis. PASTEC (Passager Technologique) studies orbital environment issues. VEGA is a transponder used to calibrate ground radars; reportedly carried on `all SPOT family satellites'.
| SPOT 4 | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1998 Mar 24 | 0146 | Launch by Ariane 40 | |
| T+03:06 Stage 1 sep | |||
| T+03:11 Stage 2 burn | |||
| T+03:46 Fairing sep | |||
| T+05:23 Stage 2 sep | |||
| T+05:38 Stage 3 burn | |||
| T+18:15 Stage 3 MECO | |||
| T+18:38 SC sep | |||