The Goddard team that NASA recently selected to build a next-generation spectrometer for Japan’s Astro-H mission has won the 2008 “IRAD Innovator of the Year” award. The Office of the Chief Technologist bestows the award annually on technologists who exemplify the best in R&D.
The team, led by Principal Investigator Richard Kelley, was chosen because of its success leveraging Internal Research and Development (IRAD) funds to enhance instrument capabilities and ultimately being selected to build the $44 million Soft X-ray Spectrometer (SXS), which will probe the motion of matter in extreme environments, investigate the nature of dark matter on large scales, and explore how galaxies and clusters of galaxies form and evolve.
“We invest in technology primarily to become more competitive winning new work,” said Chief Technologist Peter Hughes, who administers the IRAD program. “Richard’s team effectively used those investments to significantly improve his instrument, which resulted in new business for Goddard. We’re very pleased with his success and happy that our investments paid off.”
In late June, NASA selected the instrument from among 17 proposals under the Agency’s Explorer Program Mission of Opportunity solicitation. It is one of four slated to fly on Astro-H (formerly known as the New X-ray Telescope), which the Japan Aerospace Exploration Agency plans to launch in 2013.
Though similar in many respects to the X-Ray Spectro-meter that flew on Japan’s Suzaku Observatory in 2005, the new instrument will offer greater capabilities particularly in the areas of detector performance, cooling technologies, and collecting area — enhancements made possible in part by Goddard’s R&D investment programs, said Kelley.
The SXS team includes (from left to right): Peter Serlemitsos, Richard Kelley, Peter Shirron, F. Scott Porter, and Carolina Kilbourne. Christine Jhabvala, Nicholas Costen, Samuel J. Moseley, Takashi Okajima, and Yang Soong are not pictured.
“Certainly, the support we received through Goddard’s IRAD and other programs contributed to our proposal win and our ability to build an enhanced, higher-resolution instrument,” he said.
Larger Microcalorimeter Array
Chief among the improvements is the instrument’s microcalorimeter array — an IRAD-funded technology that first flew on Suzaku. With microcalorimetry, incoming X-ray photons strike the microcalorimeter’s absorbers, where their energy is converted to heat and measured. The heat is directly proportional to the X-rays’ energy, revealing much about the physical properties of the X-ray- emitting object.
To gather as many X-ray photons as possible, scientists place an array of microcalorimeters at the focus of a large X-ray telescope and cool the instrument to about one-tenth of a degree above absolute zero.
While Suzaku carried a spectrometer equipped with a 32-pixel microcalorimeter array, the SXS array is twice as large with 64 pixels, said detector developer Christine Jhabvala. More pixels mean a greater field of view, which will significantly improve measurements of the many extended sources that Astro-H will observe. Scaling up to the larger size was driven in part by a new technique for attaching large numbers of absorbers simultaneously, she said.
The cooling technology needed to measure X-ray photon heat represents another significant instrument advance. SXS will come equipped with a two-stage adiabatic demagnetization refrigerator (ADR), a mechanical cooling system that provides improved cooling capacity over the cryogenic dewars that NASA traditionally used to cool infrared and X-ray detectors. Suzaku had flown a one-stage model.
Further improvements are planned for the Goddard-developed technology, said Peter Shirron, who leads the Center’s ADR development effort. With his R&D funding, Shirron is now developing a more advanced four-stage unit — the continuous ADR — that runs around-the-clock and is capable of 30 times more cooling capacity.
“Support we’ve received through IRAD and Goddard’s Innovative Partnerships Program Office has really kept us going,” Shirron said.
The instrument’s mirror assembly also benefited from past R&D funding, Kelley said.
SXS’s mirror assembly will include as many as 1,800 curved mirror segments, nested inside a canister-type assembly. Goddard scientist Peter Serlemitsos and his co-workers will make the mirror shells of a commercial aluminum alloy sheet, which is inexpensive and very lightweight — two very important considerations for space- borne instruments.
The challenge is in accurately shaping the aluminum, then making its surface smooth enough and coating it with gold to efficiently reflect X-rays. The smoothness requirement is considerably more stringent than it is for optical telescope mirrors, he said. Using Goddard R&D funding, Serlemitsos developed a technique to replicate the smoothness of PYREX glass using a sprayed epoxy buffer layer and a thin gold layer, acting as the release agent.
“With this technology, we were able to find a niche in the field of X-ray instrumentation. We were able to keep down instrument costs and weight, which are important drivers in the field,” he said.
Goddard technologists win new work, secure follow-on funding to mature new technologies, formulate concepts, and validate new instrument concepts in flight demonstrations — successes that benefit Goddard and the scientific community as a whole.