Orbiting Earth in search of failure: NASA experiments subject electronics to harsh radiation

It’s a mission where failure will be success — and that’s exactly
what NASA engineers are hoping for.

They anticipate failures in six experiments on the NASA Space
Radiation Electronics Testbed, a payload now orbiting Earth
aboard the Space Technology Research Vehicle-1-d. The
satellite was launched Nov. 15 on an Ariane 5 rocket from French
Guiana.

Managed by the Marshall Space Flight Center in Huntsville, Ala.,
the experiments will enable engineers to better evaluate the
effects of space radiation on advanced microelectronics.
Radiation can cause trouble for printed circuit boards and other
electronic equipment on satellites.

“It may sound strange, but we’re actually hoping electronic
components will fail,” said Donna Hardage, project manager for
the NASA Space Radiation and Electronics Testbed at the
Marshall Center. “That’s the best way we can accurately know
their limits.

“We’re monitoring and evaluating several commercial
off-the-shelf electronic components to determine how they hold
up under the severe exposure to radiation,” Hardage added.

Engineers will use telemetry data received from the satellite to
improve designs for spacecraft circuitry. The experiments also
will help meet NASA’s goals of reducing costs, weight, power
requirements and production time for future spacecraft while
improving their reliability.

The experiment package is part of a joint mission involving NASA,
the U.S. Department of Defense’s Ballistic Missile Defense
Organization, the U.S. Air Force, the United Kingdom’s Defence
Evaluation and Research Agency and several other international
organizations.

The mission — planned to last for at least one year — is
corresponding with the solar maximum that occurs every 11
years — a period when solar and radiation activity is at its peak.

As it circles the Earth every 10.5 hours, the satellite passes
through the Van Allen Belts, zones of intense radiation trapped in
Earth’s magnetosphere and extending several thousands miles
into space. There, the satellite encounters the trapped proton
region and the inner and outer electron belts. Charged particles in
these belts cause serious problems for satellite operations —
such as deterioration of components and interruption of
electronic signals.

The package is about the size of a 40-quart ice chest and weighs
220 pounds (100 kilograms.)

The satellite is in a highly elliptical orbit to expose it to greater
radiation. The orbit is 385.3 miles (620 kilometers) at perigee, its
closest point to the Earth, and 24,230 miles (39,000 kilometers)
at apogee, its farthest point from Earth.

“We’re pushing these components to their limits. If they survive,
that tells us a lot. But if they fail, it tells us even more,” Hardage
said.

“All of the commercial off-the-shelf items have been tested on the
ground, but with exposure to only one energy range and just one
energy particle,” she said. ” We want to see how they respond to
continual radiation as well as events such as solar flares and
cosmic rays.”

Engineers will use the collected data to improve models for
designing and manufacturing electronics for space missions.
The investigators are expected to publish the results in the spring
of 2002.

Here are brief descriptions of the experiments:

The dosimetry experiment measures the amount of
radiation on the components. Monitoring parameters
include ionizing dose, temperature, particle energy, and
charging effects. The experiment also evaluates the
effectiveness of composite material and conformal coating
shielding technologies on the components.



The commercial off-the-shelf analog experiment
measures the impact of continual exposure to low-level
radiation and of solar flares and cosmic rays (transient
single event effects) on commercial analog devices —
those that operate or display information continuously like a
thermometer or voltmeter. Engineers hope to reduce the
uncertainties regarding performance of these devices
when exposed to space radiation.



The commercial off-the-shelf digital experiment
measures the impact of the radiation environment on
commercial digital devices, such as stacked memories,
ferroelectric memories, field programmable gate arrays
and flash electrically erasable programmable read-only
memories. Such devices are found in everyday items
ranging from cellular telephones to the cable box
connected to a television. Engineers will evaluate these
microelectronic components for future space applications.



The commercial off-the-shelf photonics experiment is
a two-part study that measures enhanced proton
displacement effects, single event transients and total
ionizing dose/displacement damage effects on high rate,
state-of the-art commercial optocouplers — devices that
bridge gaps between incompatible wire communications
systems. The engineers are also getting information from,
and evaluating components identical to those on the
Hubble Space Telescope. Hubble — one of the largest and
most complex satellites ever built — has been orbiting
Earth since 1990.



The pulse height analysis experiment measures the
radiation environment of the satellite. The device will
monitor the amount of radiation from solar flares and
cosmic rays. The data will be used to update the
engineering models for electronic components in space
applications and help to improve predictions about the rate
of these occurrences.

NASA’s Space Environments and Effects program, managed by
the Marshall Center, provides funding for government agencies to
periodically update and validate new engineering models for
electronics based on data gathered from space.

Other major participants in the program include NASA
Headquarters, Washington, D.C.; Goddard Space Flight Center,
Greenbelt, Md.; Jet Propulsion Laboratory, Pasadena, Calif.;
Langley Research Center, Hampton, Va.; and the Aerospace
Corporation, El Segundo, Calif.

The Space Technology Research Vehicle is funded by the U.S.
Department of Defense’s Ballistic Missile Defense Organization,
Washington, D.C., with development and integration performed
by the U.S. Air Force Research Laboratory, Kirtland Air Force
Base, New Mexico.

The United Kingdom’s Defence Evaluation and Research
Agency, in Farnborough, England, was responsible for the
payload integration and launch of the Space Technology
Research Vehicle-1-d.