Chuck Bednar for redOrbit.com – Your Universe Online
Typically, high-altitude scientific balloons only collect data when starlight can be detected at night, but one NASA engineer is working on a new device that may help instruments overcome the sunlight that limits their field of vision and operate before the sun goes down.
Scott Heatwole, a member of the agency’s Wallops Flight Facility (WFF) Balloon Program, is in the process of developing a low-cost precision attitude sensor or “star tracker” that would be able to locate stars and use them as points of reference in the sky during daylight hours.
Doing so would help orient instruments so that they can find their intended research targets more easily. His proposed off-the-shelf solution would also help advance the use of high-altitude research balloons, which are currently capable of carrying scientific instruments into the stratosphere and remaining aloft for several days at a time, according to NASA.
“A precision attitude sensor capable of working in the daylight would extend science operations through the day which would significantly increase the amount of science collected,” Heatwole explained. “Currently, the only precision attitude sensor available in daytime is a sun sensor, and this isn’t ideal because it provides only two axes of attitude and is not precise over a range of targets across the sky.”
He is developing his daytime star tracker to be used specifically with the Wallops Arc Second Pointer (WASP), which the agency claims would be able to use data obtained from the system to direct a balloon-borne scientific payload with incredible accuracy and stability.
WASP to change the future of star tracking
Currently, WASP is outfitted with the commonly used the ST5000 star tracker. However, NASA explains that the device is unable to image during the day, even when operating at altitudes of 120,000 feet. While it is relatively dark that high off the ground, the scattering of sunlight off the atmosphere tends to overwhelm the starlight in most star cameras, the agency explained.
While other researchers have developed similar custom star trackers capable of operating during the day, Heatwole is the first to assemble a package that also includes cameras, computers, and the algorithms required to process data and eliminate excess visible light in real time.
His tracker is comprised of a commercially available firewire camera that is attached to a lens and baffle to help filter out visible light. This allows it to sense points of reference in the near-infrared wavelength bands. A prototype of the device has flown on two WASP missions.
In the first mission, the HyperSpectral Imager for Climate Science (HySICS) collected radiance data as WASP pointed the instrument toward the Earth, the sun, and the Moon. The goal of that mission was to see what the star tracker could detect at an altitude of 120,000 feet.
The second mission carried the Observatory for Planetary Investigations from the Stratosphere (OPIS). The goal of this mission, which took place in October, was to gather time measurements of the bright gas giant Jupiter’s atmospheric structure. During this mission, Heatwole said that the algorithm did not work as expected and was unable to filter out the excess light.
However, he had no plans to abandon his project, and plans to fine-tune the algorithms over the next few months in order to eliminate the extra light experienced during the OPIS mission. After that, he plans to conduct additional tests of the star tracker during a sounding rocket flight this summer, as well as on future WASP missions scheduled for 2016 and 2017.
“We’re trying to increase the capabilities of WASP,” said Heatwole. “No company is going to go out and build this. No one is going to develop an off-the-shelf, low-cost daytime star tracker and put all the components in one package. WASP requires an attitude sensor that is capable in the daytime. That’s what we hope to create.”
—–
Follow redOrbit on Twitter, Facebook, Instagram and Pinterest.
Comments