It’s been a good year for Goddard’s Wavefront Sensing and Control Group, the band of technologists who delivered an advanced algorithm for aligning the James Webb Space Telescope’s (JWST) multiple mirror segments so that they operate as a single mirror system once the observatory begins operations early next decade.
During a demonstration with Ball Aerospace’s high-fidelity testbed telescope — a one-sixth scale model of JWST — the software performed as designed. As a result, JWST’s end-to-end optics commissioning system achieved a technology readiness level of six (out of nine) under NASA’s system for determining the maturity of new technologies. That means the software, called the Hybrid Diversity Algorithm (HDA), is ready for flight qualification testing leading up to JWST’s launch in 2013.
Other Potential Users
In addition, the U.S. military and the National Radio Astronomy Observatory have expressed interest in using the algorithm for their applications, and market research conducted for Goddard’s Innovative Program Partnerships Office by a North Carolina-based company revealed that the technology had excellent market potential across multiple industries. A private company already has contacted Dean about possible licensing, he said.
Although the group won’t use its HDA technology directly in the effort, it likely will use it as a monitoring tool to insure that the laser technology is working properly, said Bruce Dean, Group Leader for the Optics Branch Wavefront Sensing and Control Group.
While work ramps up on the new IRAD program, Dean and his team are still savoring the success of HDA, a patented technology he set out to develop 8 years ago as a NASA Co-op student from West Virginia University. The HDA algorithm solves one of NASA’s biggest technological challenges: aligning JWST’s segmented mirror so that it performs flawlessly after launch and deployment.
The JWST Challenge
Compared with other NASA observatories, JWST will fly the largest primary mirror ever deployed in space. Measuring 21.3 feet (6.5 meters) in diameter, it is significantly larger than HST’s 7.8-foot (2.4-meter) primary mirror. The much larger size is needed to gather infrared light from the first galaxies formed after the Big Bang.
However, no rocket is large enough to hold a 6.5-meter mirror if it were flown in one large piece. Therefore, the JWST team is assembling the mirror in 18 segments, which will fold like a drop-leaf table and then unfold after launch.
To make sure the segments are perfectly aligned once they deploy, the observatory will take an image of a star and transmit it to the ground. Controllers will then analyze it using eight different commissioning steps, each step handing off to the next, to determine how to properly position the individual segments to eliminate distortions in the observatory’s vision. HDA is involved in four of these eight commissioning steps, including the last step to assure a sharp, clear image. Every couple weeks, the JWST team will then repeat the last step of this process to maintain the observatory’s light-gathering prowess.
“This is a real breakthrough,” Dean said. “People would be amazed at what this algorithm accomplishes to save millions of dollars in flight system development costs. In essence we replace hardware using software.”
Nearly 2 years ago, Dean delivered the algorithm to Ball Aerospace, which adopted HDA as its primary commissioning software. During a recent demonstration, HDA proved to be the key software component that allowed JWST to achieve technology maturity level of six, as determined by an independent review board, Dean said.
With that success, Dean is now gearing up to apply the group’s know-how to other technical challenges. “Having the opportunity to build a Wavefront Sensing Group from some of the best and brightest and to see these technologies further developed for missions like JWST has been an awesome experience,” he said.
Bruce.Dean@nasa.gov or 301.286.8238
The Office of the Chief Technologist is involved in a variety of projects, missions, and technologies.