Space Technology Experiments
| Space Technology Experiments ( STEX ) | |
|---|---|
|
|
| Type: | Experimental satellite |
| Country: |
 United States
|
| Operator: | NGO |
| COSPAR-ID : | 1998-055A |
| Mission dates | |
| Dimensions: | 539.4 kg |
| Begin: | October 3, 1998, 10:04:49 UTC |
| Starting place: | VABF , SLC-576E |
| Launcher: | Taurus-1110 T-3 |
| Status: | in orbit, out of order |
| Orbit data | |
| Rotation time : | 99.4 min |
| Orbit inclination : | 85.0 ° |
| Apogee height : | 744.6 km |
| Perigee height : | 729.6 km |
The Space Technology Experiments satellite (also STEX , USA-140 or NROL-8 ) was an American technology testing satellite of the National Reconnaissance Office .
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Experiments
STEX had a total of 29 experiments on board, which should bring improvements for future missions:
- A Hall drive ( ion drive ) with 40 mN thrust.
- A solid-state disk that was the largest in space to date with 51 Gbit storage space.
- High density NiMH batteries that last longer and retain 35% more energy with less weight.
- Bumpless dispensing experiments, which should test lower shock levels for future satellites, which saves costs and weight.
- Two experimental high-performance solar panels that produced 23% more electricity than conventional solar cells.
- Lightweight, high-precision star trackers that provided valuable data for future missions in low Earth orbit and for mitigating radiation effects.
- A RAD 6000 processor with 20 MHz clock rate, the fastest in space so far, which worked without any problems and did not require a restart.
Technical specifications
The spacecraft consisted of a main body, two solar panels and was three-axis stabilized. A light precision star tracker was used to determine the satellite's position. The planned lifespan of STEX was two years.
ATEx
The ATEx experiment ( Advanced Tether Experiment , also known as USA-141 ) was a sub-satellite. It was attached to STEX with a rope. The experiment, built by the Naval Center for Space Technology (NCST), served the purpose of testing the control and survivability of two-part satellites for future missions.
ATEx again consisted of two parts: ATEx-LEB (Advanced Tether-Experiment - Lower End Body) and ATEx-UEB (Advanced Tether-Experiment - Upper End Body). In addition, ATEx should study the survivability of several compounds.
The ATEx-UEB had a dimension of 0.62 × 0.52 × 0.07 m and a weight of 11.8 kg, the ATEx-LEB one of 0.53 × 0.43 × 0.60 m. He weighed 27.6 kg. The lanyard weighed another 13.4 kg. When fully unfolded, STEX and ATEx should be more than 6 km apart.
Mission history
STEX was born on 3 October 1998, together with ATEx, on a Taurus - launcher (now Minotaur-C) from the Vandenberg Air Force Base into a low earth orbit started. On January 16, 1999 an attempt was made to separate ATEx from STEX, but this only partially worked. ATEx could only move 22 m away from STEX. An automatic protection system stopped the removal process because the tether deviated from its expected take-off angle. None of the desired goals were achieved, but STEX continued to collect valuable data for future space travel.
The STEX probe was switched off at the beginning of June 1999 due to the lower output of the solar cells.