NRL's Forward Technology Solar Cell Experiment flies as part ofMISSE5 aboard Space Shuttle Discovery mission (Forwarded)

Naval Research Laboratory
Washington, D.C.

9/19/2005

NRL Press Release 43-05r

NRL's Forward Technology Solar Cell Experiment flies as part of MISSE5
aboard Space Shuttle Discovery Mission

The Naval Research Laboratory served as the payload developer, program
manager and system integrator for the 5th Materials on the International
Space Station Experiment (MISSE5) which was launched aboard the Space
Shuttle Discovery (STS-114) on July 26. MISSE5 is part of NASA's ongoing
MISSE program.

At NRL, MISSE5 is a collaborative effort between researchers in the
Electronics Science and Technology Division and the Spacecraft Engineering
Department. Dr. Robert Walters in the Solid State Devices Branch and Mr.
Chris Garner in the Space Electronics Systems Development Branch are the
principal investigators.

MISSE5 is actually a combination of three experiments. All three
experiments are housed in a 2' x 2' metal suitcase called the passive
experiment container or PEC. The PEC was stowed in the multi-purpose
logistics module for launch on the shuttle. Once the shuttle docked to the
International Space Station (ISS), astronauts performed an extra vehicular
activity (EVA), more commonly known as a space walk, to transport the PEC
to its intended location on the ISS. The PEC was installed on an ISS
hand-rail with a special hand-rail clamp pointer mechanism. The astronauts
opened the PEC and enabled the experiment. Astronaut Soichi Noguchi
performed the EVA deployment of MISSE5. The experiment is expected to
remain on the ISS for 12 months.

Inside the PEC, the first experiment is the NRL-developed experiment is
the Forward Technology Solar Cell Experiment (FTSCE). The goal of FTSCE is
to put current and future solar cell technologies into space. Once in
space the solar cell experiments are subjected to the combined effects of
vacuum, thermal cycling, charged particle radiation, ultraviolet radiation
and atomic oxygen erosion. Within FTSCE, there are 39 solar cell
experiments, including state-of-the-art triple junction solar cells from
Spectrolab and Emcore. Thirty-six experiments will have a 32 point I-V
curve, sampled once per orbit. The remaining 3 experiments will have their
short circuit current or open circuit voltage measured.

Data acquisition for FTSCE will be performed by electronics designed and
fabricated by the NASA Glenn Research Center (GRC). The NASA GRC
electronics represent a significant technological advance in terms of
reduction of size and weight. One data acquisition board is only about 4x6
in.2 and is capable of measuring a 32 point I-V curve on four individual
solar cells, making two temperature measurements, and taking data from one
sun angle sensor. The data is beaconed down once an orbit via an amateur
radio frequency system put together by the U.S. Naval Academy (USNA).
NRL's Solid State Electronics Branch (Code 6818) was responsible for the
characterization of all of the solar cell experiments with a simulated air
mass zero, 1 sun intensity solar simulator. The Solid State Electronics
Branch is also responsible for the post-flight generation of I-V curves
from the on-orbit data.

The second experiment aboard MISSE5 is PCSat 2. The USNA under the
direction of CDR Bob Bruninga (USN Retired) assembled a RF subsystem using
commercial off-the-shelf components with selective upgrades to electronic
parts and housings. The primary transmit/receive frequencies are
435/145.825 MHz. PCSat2 provides the capability to transmit FTSCE data and
upload commands to the experiment. PCSat2 also provides a PSK-31
experiment that allows up to 20 users to correspond on a low Doppler
single side band to FM transponder.

The third experiment, also called MISSE5, was prepared by the NASA Langley
Research Center (LaRC) and GRC with contributions from a number of other
laboratories. The NASA LaRC and GRC team has transformed the outer layer
of the thermal blanket into a three and one half ounce experiment to
evaluate the in-space survivability of 200 advanced materials that are
being developed to enable future U.S. space missions. The survivability of
these materials will be established by comparing pre- and post-flight
characterization test data.

NRL' s Systems Analysis Branch (Code 8222) provided the mechanical design
and integration of the experiments into the PEC. NRL's Space Electronics
Systems Development Branch (Code 8240) designed and fabricated the
electrical power subsystem for FTSCE and PCSat2. Four strings of Emcore
ATJM solar cells provide sunlight power. Four 55-ampere-hour Lithium Ion
battery cells from Lithion, Inc., provide power while the experiment is
shadowed or in an orbital eclipse. Battery charge controls and load
distribution functions are carried out in the power control unit designed
by NRL's Space Electronics Systems Development Branch (Code 8244). This
will be the first use of high capacity, prismatic lithium-ion batteries in
a low earth orbit application.

The US Air Force Space Test Program's-DOD payload office at NASA Johnson
Space flight center served as the launch vehicle integrator.

IMAGE CAPTIONS:

[Image 1:
http://www.nrl.navy.mil/pao/PressRel...05/MISSES1.jpg (48KB)]
Dr. Walters explains to astronauts Soichi Noguchi (NASDA-Japan) and Steve
Robinson (NASA) the operation of the triple junction solar cell
experiments.

[Image 2:
http://www.nrl.navy.mil/pao/PressRel...005/MISSES.jpg (72KB)]
Position of the solar cell experiments on FTSCE.