NASA builds surprising testbed for examining X-ray navigation technologies
Contact: Lori Keesey
NASA/Goddard Space Flight Center
Pulsars have a series of surprising qualities. Like zombies, they gleam even yet they’re technically dead, and they stagger rapidly, emitting absolute and unchanging beams of deviation that are seen as flashes of light, blinking on and off during intervals from seconds to milliseconds. A NASA group has built a first-of-a-kind testbed that simulates these particular pulsations.
The pulsar-on-a-table, famous as a Goddard X-ray Navigation Laboratory Testbed, was built to exam and countenance a next-generation X-ray navigation record to be demonstrated on a dual-use instrument recently comparison as a NASA Explorer Mission of Opportunity.
“This is a singular capability,” pronounced Jason Mitchell, an operative during NASA’s Goddard Space Flight Center in Greenbelt, Md., who helped rise a tabletop-size trickery that simulates a rapid-fire pulsations that heed this surprising category of stars, deliberate a densest objects in a universe. “We indispensable a capability that would let us retire technological risks early and exam as many of a technology’s components as possible,” he said.
The trickery is validating modernized technologies for a Neutron-star Interior Composition Explorer/Station Explorer for X-ray Timing and Navigation Technology, or “NICER/SEXTANT,” for short. Slated to fly on a International Space Station in 2017, a instrument will investigate a interior compositions of proton stars mostly by observations of their pulsating next-of-kin, pulsars, and from a same platform, denote pulsar-based navigation, also called XNAV, a judgment modernized after a find of these objects in 1967.
Pulsars offer a potentially insubordinate maritime resolution since of their fast revolution and a absolute beams of light that emanate from their captivating poles. On Earth, these beams are seen as flashes of light, blinking on and off as a pulsar rotates into view. Because of their predicted pulsations, they can yield high-precision timing only like a atomic-clock signals granted by a 26-satellite, military-operated GPS.
However, distinct GPS signals, that are geared to Earth-based applications, pulsars are permitted in probably each fathomable moody regime, from low-Earth to interplanetary science, creation a record ideal for transport via a solar complement and beyond.
From a berth on a International Space Station, a NICER/SEXTANT instrument will use a 56 bundled X-ray telescopes, silicon detectors and other modernized technologies to detect X-ray photons in a pulsars’ absolute beams of light to guess their attainment times. With these measurements, a complement will tack together an onboard, totally unconstrained maritime resolution regulating specifically grown algorithms.
“X-ray navigation has a power to turn an enabling record for really low space scrutiny and an critical augmentation to NASA’s Deep Space Network” (the network of belligerent stations that promulgate with booster to make march corrections), pronounced co-developer Luke Winternitz, also of NASA Goddard, whose curriculum vitae also includes a growth of another modernized navigation technology, a Navigator receiver that captures a GPS vigilance even in low-signal environments.
With a Explorer win, a NICER/SEXTANT group will start building and integrating a telescope package and compared hardware and software.
But as with all booster missions, end-to-end contrast presents another set of challenges. “We had to have a approach to exam a technology,” Winternitz said. “We have GPS constellation simulators that make a GPS receivers consider they are in orbit; we indispensable something equivalent for an XNAV receiver.”
Mimicking Pulsar Pulsations
In essence, a pulsar-on-a-table does only that.
It leverages several Goddard-developed navigation and orbit-determination program collection and specialized hardware to impersonate a pulsar’s spin rates, a plcae in a sky, a station’s orbital parameters, and other considerations indispensable to copy a sourroundings and conditions that NICER/SEXTANT will confront when formulating a maritime solution. “You can change a lot of a parameters in a testbed and supplement hardware in a loop, to perform a full apartment of tests,” Winternitz said. “We now have a approach to take a goal judgment and exam it fully.”
A executive member of GXNLT is Goddard’s Modulated X-ray Source, that produces X-ray photons with fast varying intensity, branch on and off many times per second to copy a aim star’s pulsations. Each MXS-produced photon travels by a brief channel and impinges on a silicon-drift detector, where it receives a time stamp. The photon events are grouped into batches and processed by algorithms to remove pulse-arrival time and Doppler measurements. A set of collection afterwards uses these measurements to guess a orbital outpost’s position all indispensable to eventually delineate a maritime solution.
To ground-truth a calculations, a group will run comparisons with an onboard GPS receiver formed on a Goddard-developed Navigator receiver. Two NASA missions will use a Navigator record to acquire GPS signals in weak-signal areas. Experiments with a testbed have shown that NICER/SEXTANT, once deployed, will denote real-time calculations with sub-kilometer accuracy, Winternitz said.
“The whole indicate is to exam as we fly,” Mitchell said. “This testbed enables that.” But what is a facility’s many important attribute? It’s a fact that “it can copy a pulsar,” Mitchell said. “To my knowledge, zero in a universe can do this.”
For some-more information about a NICER/SEXTANT mission, revisit http://heasarc.gsfc.nasa.gov/docs/nicer/
For some-more Goddard record news, revisit http://gsfctechnology.gsfc.nasa.gov
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