CATS in Dragon’s Trunk Promises New Era in ISS Based Observation

CATS Graphic: Image Credit GSFC

When SpaceX made its first launch to ISS in May of 2012 as part of the history making COTS 2/3 mission, the cargo consisted almost entirely of low value, non-essential items, and for obvious reasons.

Six launches later, and for the moment the only US spacecraft supplying the ISS in the wake of the ORB-3 loss in October 2014, the Dragon spacecraft was quite a bit more heavily laden, and one of the key items en-route to the Station is the Goddard Space Flight Center’s CATS, or Cloud Aerosol Transport System instrument.

The first ISS bound experiment for Goddard, the refrigerator sized instrument rode to orbit in the Dragon’s trunk, and following extraction by Canadarm-2, will be handed over to the Japanese Experiment Module’s (JEM) remote manipulator arm in something of an ISS first, after which it will be mounted on the module’s JEM-EF (Exposed Facility) to begin the Earth monitoring mission implied by its acronym.

CATS is a follow on to NASA’s 2006 free flying CALYPSO spacecraft as well as to aerial experiments using the agency’s ER-2 high altitude research aircraft, and like them will use LIDAR to study aerosols, or suspended particulate matter.

Due the station’s unique properties however, as well as advances in the technology itself, CATS will offer an enormous advantage over its predecessors. From the tech standpoint, CATS will be able to operate in three modes, one primary mode using three different wavelengths, as well as two more experimental modes. The ability to use three different wavelengths (CALYPSO used two) is an important one, improving scientists’ ability to characterize particulate matter by source; wind born dust particles from volcanic eruptions, industrial pollution, by-products of large scale agricultural burning or even sea salt. Altogether, aerosols have a significant impact on cloud formation, which is a major, and still poorly understood element of characterizing the global ecosystem.

In addition to the use of new technology, CATS’ placement on ISS will open a new chapter in Earth observation, joining the JPL RapidScat ocean  monitoring instrument which launched aboard the September 21st CRS-4 mission. Both take advantage of the Station’s 51 degree inclined orbit which precesses, carrying it over much of the industrialized world at different times of day, a contrast to the fixed observations offered by typical science satellites.  In addition to supplying a cheap ride to orbit, a stable mounting platform and power to spare, the International Space Station also offers the advantage of its extremely robust communications infrastructure, which will provide project scientists an almost constant stream of real time data.

For all that however, CATS came in at a ridiculously low price, $15 million rather than the $100 million plus which might be expected if it were a stand alone spacecraft launched aboard a dedicated booster. Part of the savings came from the very lean Goddard team, consisting of principle investigator Matt McGill and a team of 12 members which built the instrument rather than contracting it out.  Also contributing to the savings was NASA’s Johnson Space Center, which used an expedited approval process as a sort of field test for a new model of Earth science to be conducted aboard ISS. The hope is that other field centers will follow suit, leading to full occupation of the orbiting facility’s alloted external space.

There is one other interesting detail regarding CATS and SpaceX. Given the go-ahead in 2011, CATS was originally scheduled to be launched aboard Japan’s HTV-5 spacecraft. When Japan began to hedge on the timing of that mission due to budget issues, GSFC looked to the still unproven Dragon for its ride to orbit. The change required new analysis of launch loads, pushing JPL’s RapidScat to the launchpad first. As it turns out, it wouldn’t have been a long wait in any event. The HTV-5 is scheduled to launch February 1st.

Posted in: NASA, Space Science

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