STEP - More
The TRW Inc. Space Test Experiment Platform (STEP) modular minisatellite bus has been
used by a series of missions sponsored by the US DOD Space Test Program (SMC/TEL), an
office of the Space and Missile Systems Centre, Test and Evaluation Directorate (SMC/TE).
The satellites are integrated at the Chantilly lightsat facility in VA U.S.
The satellites are discussed in order of launch.
- STEP-0 was launched on the 13th of March 1994 on the first Taurus launcher carrying a
number of payloads too small to justify a dedicated satellite mission. Payloads were to
test technology for autonomous, survivable satellites. The bus measures 1.12 x 1.78m,
weighs 488kg, and generates 450W power from two deployed wing solar panels. It is 3-axis
stabilised, has S, C and X-band communication links, and employs four 1lb hydrazine and
two 33lb Delta-V thrusters with 170lb tank capacity. The design life is 18 months. Amongst
the 10 instruments carried are two laser sensors, Dual cone sensors, Radar Illumination
Verification System, and an advanced lightweight GPS sensor. The satellite is three axis
(artist impression)[STEP-0 at TRW]
- STEP-2 (P91-2)
- STEP-2 (1994-029A) was launched on a Pegasus launcher on the 19th May 1994. It did not
attain the exact planned orbit of 830x830km inclined at 85 degrees, but ended up in an 834
x 606 orbit inclined at 81.9 degrees. It carries an US Air Force experiment aiming to
improve radio communications. It carries just one of the standard STEP units and includes
a steerable dish antenna, a wide beam bifilar helix, UHF antennas S-band and L-band links,
and a GPS system. The satellite is three axis stabilised using a stabilised pitch momentum
bias system. It employs four paddle-wheel deployed solar panels providing 95W orbit
average, 40W for experiments. The satellite has a 12-sided cylindrical base, measuring
1.17m x 1.51m and weighs 180kg. Design life is 1 year.
One of the planned experiments was to separate adjacent, overlapping cochannel
- STEP-1 (P90-1)
- STEP-1 carried instrumentation to investigate ionospheric effects on radio
communications and to improve atmospheric drag models, however the first flight on the
Pegasus XL which carried it on the 27th June 1994 failed. The satellite carried a range of
six 5m long deployable antennas and booms. The spacecraft was 3-axis stabilised and the
mission life time was to be three years.
- STEP-3 (P92-2)
- STEP-3 was carried on the second flight of the Pegasus XL, which failed on the 22nd of
June 1995. It carried a host of technology demonstrations including computer memory
experiments, and advanced materials and sensors evaluation. It weighed 268kg and would
generate 132W from its solar panels. It only employed the core module of the STEP bus.
Picture (right) courtesy of CTA.
- The fourth spacecraft in the series was launched on the 22nd
October 1997, but controllers failed to establish contact. This is believed to have been
due to a failure of a solar array to deploy.
- TSX-5, (P95-2),
- Following on from four previous STEP missions, the 250kg Tri Service Experiment mission
5 mission by the Space Technology Program (STP) at the Space and Missiles Centre, Test and
Evaluation (SMC/TELS) at Kirland AFB, New Mexico was launched on the 7th June from VAFB on
a Pegasus-XL into a 406x1706km orbit inclined at 69 degrees. The satellite was procured
from CTA Space Systems (now ORBITAL), costing US$85m, and uses the LEOSTAR bus based on
the earlier STEP missions. It carries two all-service payloads. STRV-2 is BMDO sponsored
vibration suppression and infra-red imaging payload with collaboration from UK DERA. This
is to image aircraft at perigee and then downlink data via laser communications link.
CEASE (Compact Environmental Anomaly Sensor) is a spacecraft radiation and charging sensor
sponsored by Phillips Lab Geophysics Lab.
- [TSX at SMC][TSX-5]