In Space, What's On The Outside Matters

September 15, 2014

Image Caption: A view of Earths atmosphere from the International Space Station during Expedition 23 illustrates the unique vantage point the orbiting laboratory provides for externally mounted instruments. Credit: NASA

Jessica Nimon, International Space Station Program Science Office/NASAs Johnson Space Center

We all know that its whats on the inside that counts, right? But sometimes whats outside can be just as important. At least thats the case with the International Space Station (ISS) and the collection of external instruments soon to join those already operating in orbit.

Moving at 17,500 miles per hour and operating around 240 miles above Earth, the space station circles at a 51.6 degree inclination north and south of the equator, offering a unique platform to mount research equipment. The space stations precessing orbit circles the globe 16 times daily to cover more ground at different times of day, while other satellites follow a sun-synchronous orbitcrossing the equator at the same local time every revolution. For this reason, data from station-mounted instruments can complement those gathered from similar satellite missions to fill in gaps for greater scientific returns.

Station instruments range from those looking for answers to the universe, such as the Alpha Magnetic Spectrometer (AMS)the largest of the externalsto those looking Earthward, providing remote sensing data. These devices rely not only on the angle and speed of the spacecraft, but also the space stations power, data and thermal support with one-of-a-kind real estate.

These are premium locations, as space in space is limited. Deployment locations on station are valuable because a sensor can reside there and generate data without project teams having to build and launch a dedicated satellite spacecraft. As of July 2014, there are 13 external locations in use aboard the orbiting complex, leaving 10 spots for new technologies. Here are a few of the latest devices planned to join this distinctive community.

The Multi-User System for Earth Sensing (MUSES), currently being developed by Teledyne Brown Engineering, Inc., is a precision-pointing platform that will mount externally to the space station. The platform will be capable of hosting up to four Earth-observing instruments simultaneously. MUSES is scheduled to launch aboard an uncrewed Japanese cargo HTV5 spacecraft in 2015. As part of a collaboration with Teledyne, the German Aerospace Center (DLR) will provide the first instrument on MUSES: the DLR Earth Sensing Imaging Spectrometer (DESIS). Teledyne and its partners will be able to use data from DESIS and future instruments aboard the MUSES platform for a variety of commercial, scientific and humanitarian applications.

Soon joining the efforts of the AMS on station is the Calorimetric Electron Telescope (CALET). This instrument is an astrophysics mission searching for signatures of dark matter. It will provide the highest energy direct measurements of the cosmic ray electron spectrum to help researchers observe discrete sources of high energy particle acceleration. Specifically, CALET will focus on Earths local region of the galaxy, and its location aboard the station will allow for observations unhindered by Earths atmosphere, which can impact readings.

The goal of CALET is to address questions of high energy astrophysics. For instance, what is the origin of cosmic rays? How do they accelerate and propagate? The instrument also will search for the existence of dark matter and nearby cosmic-ray sources. CALET is scheduled to launch to the space station on HTV5 in 2014 and is sponsored by the Japan Aerospace Exploration Agency in collaboration with the Italian Space Agency.

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In Space, What's On The Outside Matters