NASA's GPM observatory completes first dry run

Oct 18, 2012 by Ellen Gray
Engineers check on the GPM spacecraft after successful completion of its first comprehensive performance test. The silver disc and drum (center) is the GPM Microwave Imager, and the large block on the base is the Dual-frequency Precipitation Radar. The tall golden antenna is the High Gain Antenna for communications. Credit: NASA

(Phys.org)—NASA's Global Precipitation Measurement (GPM) Core Observatory satellite went through its first complete comprehensive performance test (CPT), beginning on Oct. 4, 2012 at NASA's Goddard Space Flight Center in Greenbelt, Md. The testing ran twenty-four hours, seven days a week and lasted ten days as the entire spacecraft was put through its paces.

"This is the first time we've gotten to see the observatory all put together, running the way it's supposed to be running in flight," said CPT Lead Peter Gonzales, of NASA Goddard. "The CPT is the test that verifies that the observatory can do everything we designed it to do," he said. He spent months talking with each team that engineered the spacecraft's subsystems and two instruments, the GPM (GMI) and the Dual-frequency Precipitation Radar (DPR), to design the tests that would evaluate how the GPM spacecraft functions as a whole.

"When the observatory's flying on-orbit, all of the subsystems are operating together. We're not running a single subsystem in isolation," said Gonzales. "We want to see all the subsystems work together. We want to see if we're running a test on the RF [] system, if it's being affected by the power system and vice versa."

In the Goddard clean room where the GPM Core Observatory was assembled, the spacecraft was oriented the way it would be if it were flying in space. It's about the size of a small fire truck but twice as heavy. During the test, the scanning antenna of the GMI, built by Ball Aerospace Corp. in Boulder, Colo., rotated in place as it would in orbit to collect data, the High Gain Antenna for communications inched around to orient toward a simulated receiver, and the mechanisms for the , which were not attached, turned as if tracking the sun.

In the control room next door, more than 20 engineers occupied every workstation where telemetry data from the tests streamed by lightening fast on their screens. Each subsystem and instrument was represented by the engineers that built it to make sure everything was going as expected, including a team from NASA's partner the Japan Aerospace Exploration Agency (JAXA) that built the DPR and will launch the GPM Core Observatory on a Japanese H-IIA rocket from an island in southern Japan.

"There are some 30 odd units being tested," said Candace Carlisle, Deputy Project Manager for GPM at Goddard. Every subsystem on the observatory, from propulsion to the two instruments, went through the process of being turned on and/or deployed after launch and then run through every function, she said.

Each test was run more than once since almost all of GPM's systems and instruments are redundant in case of failure in orbit. The electronics have an A-side and a B-side with two identical computers, though only one is active at a time. If the A-side fails, or in some cases if even a single A-side subsystem fails, the B-side can take over.

The comprehensive test went well, said Gonzales. They found the expected small hiccups that are normal when an observatory is first brought online as a unit, but no hardware problems or anything that would prevent them from moving forward, he said.

As the test progressed, the engineering teams were learning the nuances of how the spacecraft runs, said Gonzales, which is essential to know before going into the thorough environmental testing scheduled to begin in November 2012. In environmental testing, the GPM Core Observatory will be pushed to its limits as it goes through the rigors of the extreme temperature changes and electromagnetic interference it might experience in space, and the vibration and noise levels it will encounter during launch. The results of the comprehensive testing will serve as a baseline to compare to the results of the environmental tests.

The GPM mission is an international satellite mission that will set a new standard for precipitation measurements from space. The observatory will collect advanced measurements of rain and snow that will be combined into a global data set every three hours. The GPM observatory is scheduled to launch in early 2014. GPM is a joint mission between NASA and the Japanese Space Agency, JAXA.

Explore further: Red moon at night; stargazer's delight

More information:
www.nasa.gov/gpm
gpm.nasa.gov/

add to favorites email to friend print save as pdf

Related Stories

Handover of Japan-built radar to NASA

Apr 04, 2012

On March 30, the Japan Aerospace Exploration Agency (JAXA) officially handed off a new satellite instrument to NASA at Goddard Space Flight Center, Greenbelt, Md. The Dual-frequency Precipitation Radar (DPR) ...

Spaceborne precipitation radar ships from Japan to U.S.

Feb 09, 2012

(PhysOrg.com) -- Japanese scientists and engineers have completed construction on a new instrument designed to take 3-D measurements of the shapes, sizes and other physical characteristics of both raindrops ...

Recommended for you

Astronauts to reveal sobering data on asteroid impacts

2 hours ago

This Earth Day, Tuesday, April 22, three former NASA astronauts will present new evidence that our planet has experienced many more large-scale asteroid impacts over the past decade than previously thought… ...

Rosetta instrument commissioning continues

2 hours ago

We're now in week four of six dedicated to commissioning Rosetta's science instruments after the long hibernation period, with the majority now having completed at least a first initial switch on.

Astronaut salary

3 hours ago

Talk about a high-flying career! Being a government astronaut means you have the chance to go into space and take part in some neat projects—such as going on spacewalks, moving robotic arms and doing science ...

Red moon at night; stargazer's delight

22 hours ago

Monday night's lunar eclipse proved just as delightful as expected to those able to view it. On the East Coast, cloudy skies may have gotten in the way, but at the National Science Foundation's National Optical ...

Meteorites yield clues to Martian early atmosphere

Apr 16, 2014

(Phys.org) —Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published ...

User comments : 0

More news stories

A sharp eye on Southern binary stars

Unlike our sun, with its retinue of orbiting planets, many stars in the sky orbit around a second star. These binary stars, with orbital periods ranging from days to centuries, have long been the primary ...

Hubble image: A cross-section of the universe

An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range ...

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Astronaut salary

Talk about a high-flying career! Being a government astronaut means you have the chance to go into space and take part in some neat projects—such as going on spacewalks, moving robotic arms and doing science ...

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...