1993-026A
Alexis, the Array of Low Energy X-ray Imaging Sensors, was Space Test Program flight P89-1B. It was also known as ISES (Independent Space Experiment System). Alexis was developed by the Los Alamos National Laboratory (LANL) as part of its program to maintain capability to monitor nuclear explosions, and its main payload was six wide field X-ray telescopes to study the X-ray emission from the interstellar medium. A second LANL experiment, Blackbeard, was carried to study ionospheric propagation. A third experiment, the US Navy VSUME, was also carried, possibly on the Pegasus third stage.
Each of the six Alexis telescopes has a 0.128m diameter Cassegrain normal incidence multilayer spherical primary mirror with a focal length of 0.13m. The telescopes operate in the 100-200A band.
The 113 kg satellite was built by Aero Astro Inc. of Herndon, Virginia. The satellite was a 1.0m box with 4 panels.
Alexis was launched by Pegasus on 1993 Apr 25 over the Point Arguello Warning Area on the Western Test Range. During second stage burn, a solar panel was broken loose from its mounting by vibration. The satellite reached orbit but was unable to orient itself and fell silent. It was feared that the mission was a total loss, but over a month later a weak signal from the satellite was found. Repeated passes over the next few months allowed LANL scientists to regain full control of the spacecraft and orient it to get adequate solar power.
In 1999 because of low power, the Alexis telescopes were reduced to low voltage and run as a particle detector, during solar max when the background was high. In 2002, some of the telescopes were again being tested at high voltage.
| Alexis | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1993 Apr 25 | 1244 | NB-52 takeoff from Edwards AFB | |
| 1356 | Pegasus drop 13.3 km over PAWA | ||
| 1356 | Pegasus ignition 5s after drop | ||
| 1357 | Stage 1 sep T+90s | ||
| Stage 2 sep | |||
| 1358 | Fairing sep T+148s | ||
| 1402 | Solar panel loose T+380s | ||
| 1405? | Stage 3 burn | ||
| 1406? | Stage 3 burnout | ||
| 1407? | Stage 3 sep | 100.69 740 x 833 x 70 | |
| 100.69 749 x 844 x 70 | |||
| 1993 Jun 2 | First telemetry contact | ||
| 1993 Jun 30 | Second comm pass | ||
| 1993 Jul 5 | Full comms regained | ||
| 1993 Jul 11 | Blackbeard ops begin | ||
| 1993 Jul 30 | 100.69 747 x 835 x 69.93 | ||
| 2002 Mar | Still operating | ||
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