February 9, 2014
WASP Gives NASA’s Planetary Scientists New Observation Platform
April Flowers for redOrbit.com – Your Universe Online
High-altitude balloons have long been used by scientists who study the Earth, the sun and the stars to gain a better view of their targets by carrying their telescopes far into the stratosphere. For planetary scientists, however, this doesn't work, as they need a highly stable, off-the-shelf type system that could accurately point their instruments and then track planetary targets as they move around in the solar system.
A new pointing system, the Wallops Arc Second Pointer (WASP), has been developed by scientists at NASA's Wallops Flight Facility. WASP can point balloon-borne scientific instruments at targets with sub arc-second accuracy and stability. Later this year, a planetary scientist interested in finding less-expensive platforms for observing Jupiter and other extraterrestrial bodies intends to take the device for a test drive.
"Arc-second pointing is unbelievably precise," said David Stuchlik, the WASP project manager. "Some compare it to the ability to find and track an object that is the diameter of a dime from two miles away."
WASP, designed to be a highly flexible, standardized system capable of supporting many science payloads, will allow planetary scientists to focus on instrument development. In the past, they have had to develop their own pointing systems, raising the cost and increasing the time from concept to actual project completion. Because of the potential WASP has shown, the project has received funding from NASA's Science Mission Directorate to further enhance the new capabilities as a standard support system.
WASP was first tested in 2011, then again in 2012. Most recently, a September 2013 flight took place in Fort Sumner, New Mexico, during which a 30-story balloon lifted an engineering test unit of the HySICs (HyperSpectral Imager for Climate Science) to an altitude of nearly 122,000 feet. Far above the majority of Earth's atmosphere, WASP precisely pointed HySICs so that it was able to measure Earth, the sun and the moon.
Greg Kopp of the University of Colorado's Laboratory for Atmospheric and Space Physics developed HySICs, which collected radiance data for nearly half of its 8.5-hour flight. This flight demonstrated improved techniques for future space-based radiance tests. The imager is being prepared for another flight this September.
September will also see the inaugural flight for the Observatory for Planetary Investigations from the Stratosphere (OPIS). This flight is important because very few planetary scientists have used less-expensive balloon craft to fly their instruments in the past.
"Planetary scientists really haven't been involved in balloon payloads," said OPIS Principal Investigator Terry Hurford. "Planetary targets move with respect to the stars in the background. And because you need to track them to gather measurements, you need a system that can accurately point and then follow a target. These challenges are why planetary scientists haven't gotten into the balloon game."
The tolerances aren't as tight for other disciplines because the targets are either large, like the sun, or plentiful, like the stars. This makes it easier to target an object and then maintain a lock on it.
Hurford plans to demonstrate that WASP is just as effective for planetary science when OPIS flies high above Earth's surface to study Jupiter and planets beyond the solar system.
Funding from the Goddard Internal Research and Development program will be used to repurpose a telescope mirror originally built to calibrate the Goddard-developed Composite Infrared Spectrometer now flying aboard NASA's Cassini mission. Hurford is also using NASA support to upgrade WASP's existing avionics system to assure planetary tracking and expand its ability to follow targets above 25 degrees of elevation.
OPIS will also launch from Fort Sumner. The 24-hour mission will allow Hurford to gather time measurements of Jupiter's atmospheric structure, provided stratospheric winds cooperate. Other objectives of the mission include observing a transit of an extrasolar planet and the rotation of an asteroid.
"Time for planetary observations on ground-based observatories is difficult to obtain," Hurford said. "Moreover, high-altitude balloons above 95 percent of the Earth's atmosphere allow for observations in the ultraviolet- and infrared-wavelength bands, which aren't possible with ground-based telescopes. High-altitude balloons offer us a unique, low-cost platform to carry out our planetary observations. This effort provides us with a unique opportunity to build a capability that we can leverage for future opportunities. WASP gives us a new platform," he said.