CATS instrument to launch on CRS-5 and measure particulates in atmosphere
The fifth of twelve planned Commercial Resupply Services missions launched by SpaceX, CRS-5, is now scheduled to launch no earlier than Jan. 6 2015. When it takes to the skies, it will carry with it not only necessary supplies for the crew on board the International Space Station (ISS), but also the Cloud-Aerosol Transport System, or CATS. This instrument: “uses a light detection and ranging (LiDAR) system to measure the location, composition and distribution of pollution, dust, smoke, aerosols and other particulates in the atmosphere,” according to NASA’s website.
CATS is not a free-floating satellite, but instead it will be mounted to the exterior of the Japanese Experiment Module, which is called Kibo, meaning “hope” in Japanese. This will be done in partnership with the Japan Aerospace Exploration Agency (JAXA ). If it does well, it can be scaled up to be a traditional satellite payload.
CATS has the ability to provide range-resolved measurements, which means it can distinguish between targets that are close together in bearing but at different ranges (essentially, different distances) from the instrument. It uses a laser with a high repetition rate that operates at three wavelengths: 1064, 532, and 355 nanometers (nm).
The 1064- and 532-nm wavelengths are already used by NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission. However, the addition of the 355-nm wavelength adds the opportunity for observing in greater detail, making it easier to tell different types of particles apart. The instrument also has highly sensitive detectors that can count even individual photons.
“You get better data quality because you make fewer assumptions, and you get, presumably, a more accurate determination of what kind of particles you’re seeing in the atmosphere,” said research scientist Matt McGill and principle investigator for CATS at NASA’s Goddard Space Flight Center in Maryland.
There is some concern that this third laser is prone to being contaminated.
“If you get contamination on any of your outgoing optics, they can self-destruct, and then your system’s dead,” McGill said. “You end up with very limited instrument lifetime.”
Thus, part of the mission is also dealing with that risk, and seeing how the instrument fares in space. Mounting it to the ISS is a way to cut costs in this process.
As for the laser’s high rate of repetition, CATS can again be compared with CALIPSO, which fires 20 laser pulses per second, each at 110 milliJoules of energy. Conversely, CATS will fire 5,000 pulses every second, though each at about 1 milliJoule. Universe Today has noted that once CATS is mounted to the ISS and when the station passes through Earth’s shadow, it may be possible to spot the instrument from Earth despite the relatively low-energy pulses it will be emitting.
With its capabilities, CATS will be able to measure details of the cloud and aerosol layers like “layer height, layer thickness, optical depth, extinction, and depolarization-based discrimination of particle type,” according to NASA. Further, the agency’s website states that “the impact of clouds and aerosols (e.g., pollution, dust, smoke) on a global scale with regards to energy balance and climate feedback mechanisms is not yet fully understood. A better understanding of cloud and aerosol coverage and properties is critical for understanding of the Earth system and its associated climate feedback processes.”
The usefulness of CATS and similar instruments is partly illustrated by the 2010 eruption of the Eyjafjallajökull volcano in Iceland and the many grounded aircraft and stranded travelers affected by it. The particles in the ash cloud had the potential to seriously damage the engines of aircraft in flight. Now, however, NASA will be able to better track such particles from space as they spread through the air below.
The ISS has a helpful orbit for this sort of experiment as it already “passes over and along many of the primary aerosol transport paths within the atmosphere” and “permits study of diurnal (day to night) changes due to the effects of aerosols and clouds in the atmosphere – something other Earth Science satellite cannot readily obtain given their orbits,” NASA stated.
The current version of the mission is expected to last six months at the bare minimum, and three years maximum. It is one of five Earth science missions that NASA scheduled to launch in 2014 and, along with SMAP, one of two now scheduled for Jan. of 2015 instead.
Want to learn more about this promising Earth science mission? Be sure to check out the video below released by NASA Goddard and the CATS team.
Video courtesy of NASA Goddard
Rae Botsford End is a freelance writer and editor whose primary work currently is writing technical white papers, contributing to SFI, and working on a speculative fiction novel that she hopes to have published soon.
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