TRMM and ETS-VII have been launched
Craig Cholar (3432P@VM1.CC.NPS.NAVY.MIL)
Thu, 27 Nov 97 14:52:03 PST
Florida Today Space Online reports that the TRMM (Tropical Rainfall
Measuring Mission) and a Japanese rendevous and docking experiment
were launched at 2127 UT 11/27.
Here's some background information about the pair of satellites that will
be docking and undocking repeatedly for the next 1.5 years. They should
be interesting to observe for those of us who aren't too far north. The
following information is taken from the Japanese space agency website at
http://yyy.tksc.nasda.go.jp/Home/News/News-e/64trmm.htm
Rendezvous-docking Technology Experiment
The ETS-VII is composed of two satellites, the chase satellite dubbed
Hikoboshi and the target satellite dubbed Orihime. One of its
objectives is to perform a technology experiment involving the
automatic/remote control rendevous-docking of two unmanned space
vehicles. This will be the world's first attempt at such an experiment.
In this experiment, the chase satellite is programmed to move 9
kilometers away from the target satellite after separating from it in
space and then approach the target satellite for docking. To ensure a
successful rendezvous-docking of two unmanned space vehicles, a
navigation system which can measure and estimate their relative
positions and speeds is necessary.
In the forthcoming experiment, three kinds of navigation instruments
will be used depending on the distance between the two satellites. The
GPS receiver will be used for distances from 9 kilometers to 600 meters,
the rendezvous radar for distances from 600 meters to 2 meters, and the
proximity sensor for distance less than 2 meters. The chase satellite
is planned to automatically determine its target orbit by computing the
distance and gradually increasing its control precision while continuing
orbit control. In the final stage, the chase satellite will approach
the target satellite at a speed of a few centimeters per second for
rendezvous-docking.
During the one-and-a-half-year scheduled experiment period, ETS-VII will
conduct a sequence of seven flight tests from separation to docking.
Through this experiment, NASDA expects to acquire the basic
rendezvous-docking technologies in such fields as instrumentation,
navigation, guidance, and flight control.
Craig Cholar 3432P@VM1.CC.NPS.NAVY.MIL