Wednesday, June 4, 2014

NASA ICESat-2 satellite Box structure under construction

An engineer checks ICESat-2's box structure, shortly after its arrival in a NASA clean room in May. 

Over the next two years, engineers and technicians will attach electronics, optics, lasers, a telescope and more to the box, testing its function at each step. 

Credit: NASA's Goddard Space Flight Center /Kate Ramsayer

To build a satellite that will measure all the bumps and dips of our dynamic Earth, engineers started with a black box, built of a composite honeycomb material to make it as light as possible.

The structure was precisely manufactured with an opening to allow lasers to beam to Earth, and other windows sized for a telescope that will capture photons that bounce off our planet and return to the satellite.

The box was measured and marked to denote where the assembly of aligned mirrors, electronics, lasers and photon detectors would be attached.

It must be tough enough to handle the rigors of a rocket launch and years in a harsh space environment; here on Earth, the box structure must be hardy enough to withstand tests engineers use to simulate those conditions.

The box structure at the core of the Ice, Cloud and land Elevation Satellite-2 (ICESat-2), instrument was delivered to a clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in May.

A team of 250 engineers, fabricators and scientists has now started the official integration and testing stage of the laser instrument.

"There's lots of activity, we're moving from looking at all the different subsystems, to looking at the overall system coming together."

"It's really exciting to move forward into that realm," said Cathy Richardson, instrument manager with the ICESat-2 mission. The team will have a half-dozen components ready for delivery in June.

"It's not just a drawing. It's an actual, real piece of hardware, that's getting tested and showing that it's meeting requirements."

ATLAS Assembly
ICESat-2's instrument, called the Advanced Topographic Laser Altimeter System (ATLAS), will measure the elevation of Earth's surfaces, from ice sheets to forests to oceans.

Its six beams will generate a more detailed elevation portrait than single beam of original ICESat-2, which flew from 2003 to 2009, and with the beams paired, scientists will be able to measure surface slope and better calculate height changes.

To measure elevation, ATLAS beams light with a green laser that pulses 10,000 times a second. Only a few photons will bounce off the surface and return to the satellite, but an incredibly sensitive detector counts those that do come back.

Using the time of the photons' return trip, the speed of light and some geometry, scientists can determine the distance the photons traveled and, therefore, the height of Earth below the satellite's orbit.

ATLAS will provide scientists with measurements that create a global portrait of Earth's elevation, and will gather data that can precisely track change, including melting glaciers and thinning sea ice.

Credits: Satellite image courtesy of Orbital Earth image illustrating AMSR-E sea ice courtesy of the NASA Scientific Visualization Studio

"ICESat-2 will revolutionize our understanding of ice sheet and sea ice changes and processes," said Thorsten Markus, ICESat-2 project scientist.

"I think it's one of the most exciting missions out there. There's so much opportunity for real discoveries."

The satellite will observe Earth in a new way, he said, which makes it technically challenging. But this also opens the door for discoveries not yet imagined.

After years of calculations and computer models and discussions, Markus said, it's exciting to see the hardware come together.

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