America
New NASA daytime star tracker soon
Washington, Jan 29
NASA engineers are
developing a precision attitude sensor or star tracker that would be
able to locate stars during daylight hours.
The team at NASA's
Wallops Flight Facility (WFF), located on Virginia's Eastern Shore, is
working on a low-cost, off-the-shelf solution to overcome the challenges
of collecting data in daylight, the US space agency said in a
statement.
The star tracker is being developed specifically for
the Wallops Arc Second Pointer (WASP) which would use the star tracker's
data to point a balloon-borne scientific payload with incredible
accuracy and stability.
Currently, WASP usually employs the commonly used ST5000 star tracker.
However, this device cannot take images in the daytime even at 120,000 feet where scientific balloons operate.
Though
relatively dark at those altitudes, the scattering of sunlight off the
atmosphere can overwhelm the starlight in most star cameras.
"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," explained engineer Scott
Heatwole.
Currently, the only precision attitude sensor available in daytime is a sun sensor.
"This
is not ideal because it provides only two axes of attitude and is not
precise over a range of targets across the sky," he noted.
According
to Heatwole, his daytime star tracker consists of a commercial firewire
camera attached to a lens and baffle that help filter out visible
light, allowing it to sense points of reference in the near-infrared
wavelength bands.
In 2014, a prototype of the device flew on two WASP missions.
The
first, the flight of 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 was to see what the star tracker saw at 120,000 feet.
The
second WASP mission, launched a couple months later in October, carried
the Observatory for Planetary Investigations from the Stratosphere
(OPIS).
Its mission was to gather time measurements of Jupiter's
atmospheric structure - a challenge for the new star tracker because the
gas giant is a bright object.
In the coming months, the team
plans to fine-tune the algorithms to eliminate the extra light
experienced during the OPIS mission and then retest the technology
during a sounding rocket flight this summer and additional WASP missions
in 2016 and 2017.