The US Air Force's first Advanced EHF communications satellite was launched on Aug 14, 2010. AEHF 1 is a Lockheed Martin
A2100M satellite with a launch mass of around 6200 kg. The AEHF constellation's SHF and EHF communications payloads will replace
the Milstar satellite system launched in the 1990s.
AEHF 1's Lockheed Martin/ULA Atlas V launch vehicle AV-019 was a model 531 variant with three strapon solid motors; the
first burn of the Centaur upper stage reached a 167 x 1281 km x 27.8 deg orbit at 1121 UTC. Centaur restart at 1129 UTC pushed
AEHF 1 into a 221 x 50179 km x 22.2 deg deployment orbit. Large burns with the liquid bipropellant apogee thruster was intended
to raise the orbit initially followed by several months of burns from AEHF 1's Hall-thruster electric propulsion system. However,
the bipropellant thruster cannot be operated and instead a series of small burns with a lower thrust monopropellant hydrazine
engine, using the same hydrazine tank, will be needed.
Many A2100 class satellites have used AMPAC's LEROS 1 engine, but AEHF 1 uses a different brand of apogee thruster, the
BT-4 developed by Japan's IHI Aerospace. This thruster is also flown on Orbital's Star 2 satellites. Investigation has not yet
revealed whether the fault is in the thruster itself or some other part of the propulsion system that interacts with the thruster.
According to the SeeSat list, hobbyists have tracked AEHF following six hydrazine burns to date; on Sep 7, 2010 AEHF 1 was
in a 1146 x 49994 km x 20.0 deg orbit; on Sep 20 it was in a 4546 x 49981 km x 15.4 deg orbit.
Constellation of 3 plus 1; will replace the Milstar system. This satellite's main engine failed right after launch, stranding
it in a transfer orbit. It may reach its GEO orbit by summer 2011.
During late March to late April, 2011 the US Air Force's AEHF 1
communications satellite raised its orbital period from 23 hours to 25
hours, passing briefly through the geosynchronous range. AEHF 1 was
launched in 2010 Aug to a supersynchronous transfer orbit of 249 x 50019
km x 22 deg; after failure of its main propulsion system, electric
thrusters have been used to slowly raise the orbit to its current 22923
x 51539 km x 7.1 deg. Once the perigee has been raised to the 35780 km
or so needed for geostationary orbit, the apogee will be lowered to
match and the satellite will return to geosynchronicity.
AEHF-1, took nearly 17 months to achieve its final intended orbit, after debris in an onboard fuel-line impeded the use of its
main spacecraft engine. After some 500 firings of its small electrical maneuvering thrusters, the spacecraft team wound up
performing one of the great satellite rescues to date, as AEHF-1 was declared ready to enter service as of January 2012.