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STEX (with ATEx attached) [Lockheed Martin]

The STEX (Space Technology Experiments) satellite carried 29 new technologies intended to result in lower cost and higher performance spacecraft for future missions. Among the technologies were

  • An electric propulsion engine from the Naval Research Laboratory (Russian-derived) Xenon Hall-effect electric thrusters capable of delivering 40 mN of thrust
  • a 51 Gbit solid-state data recorder. The largest solid state recorder in space (51 Gbits) was fully checked out and also performed perfectly.
  • high-density NiH batteries designed to last longer and provide 35% more energy with less weight.
  • ATEx (Advanced Tether Experiment), a 6 km tether with TiPS heritage was to be deployed as a separate sub-satellite. Frangibolts were used on the mission for shockless deployment of the spacecraft and tether.
  • Shockless separation mechanisms that will pave the way for future satellites to be designed for extremely low shock levels, saving cost and weight.
  • Experimental high efficiency solar array concentrators focused 70% more light on the arrays than standard systems. Advanced dual junction solar cells provided 23% more power than standard solar cells.
  • Lightweight, high accuracy autonomous star trackers provided valuable data on their operation in low earth orbit and how to mitigate radiation effects.
  • A 20 MHz RAD 6000 processor, the fastest in space, performed flawlessly and required no reboots.

The spacecraft was comprised of a body shell and two tracking solar panels. A blowdown liquid propulsion system was carried. The spacecraft was three-axis stablized. A lightweight precision star tracker was used to determine satellite pointing. The planned lifetime of STEX was two years

On 16 January 1999, ATEx was deployed, but failed. It was deployed but its two masses separated only by 22 m.

The STEX spacecraft was turned off in early June 1999 due to degradation of its conventional solar arrays.

Note: The NROL designations refer to the launch, not to the payload.

Nation: USA
Type / Application: Experimental
Operator: NRO
Contractors: Lockheed Martin Astronautics (Denver)
Equipment: ?
Configuration: ?
Propulsion: TAL-D55 plasma engine
Power: 2 deployable solar arrays, batteries
Orbit: 750 km × 766 km, 85.0
Satellite COSPAR Date LS Launch Vehicle Remarks
STEX (USA 140, NROL 8) 1998-055A 03.10.1998 Va 576E Taurus-1110 with ATEx-UEB, ATEx-LEB

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