In Space, What's on the Outside Matters

    HOUSTON, TX, September 16, 2014 /24-7PressRelease/ -- We all know that it's what's on the inside that counts, right? But sometimes what's outside can be just as important. At least that's 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 station's precessing orbit circles the globe 16 times daily to cover more ground at different times of day, while other satellites follow a sun-synchronous orbit--crossing 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 externals--to those looking Earthward, providing remote sensing data. These devices rely not only on the angle and speed of the spacecraft, but also the space station's 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 Earth's local region of the galaxy, and its location aboard the station will allow for observations unhindered by Earth's 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.

The Cosmic Ray Energetics and Mass (CREAM) investigation, like CALET, will help researchers in their quest to understand the nature of cosmic rays. CREAM's instruments measure the charges of cosmic rays ranging from hydrogen up through iron nuclei, over a broad energy range. The instrument, which also operated aboard balloons in the past, will now have access to readings unhindered by the atmosphere. The result is the chance for longer exposures to cosmic rays--as CREAM operates for three years aboard station--and a purity in measurements not possible from balloon-borne missions.

ISS-RapidScat, which is short for Rapid Scatterometer, is one of the most economical of the upcoming external instruments--it was built from spare parts. This sensor uses the echo of low-energy microwaves that safely bounce off the surface of Earth's waters to monitor ocean winds from the space station. Researchers will use ISS-RapidScat data to cross calibrate observations from similar space-borne sensors on polar-orbiting satellites to help monitor weather and marine forecasting. ISS-RapidScat can help with predicting large-scale climate changes or isolated severe storms, such as hurricanes, by adding data to existing weather math models. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the project, which is scheduled to travel to the space station this year. You can learn more about ISS-RapidScat in this video.

Another developmental sensor planned for station is the Cloud-Aerosol Transport System (CATS). Using three-wavelength laser technology, this instrument will measure the distribution of aerosols--tiny airborne particles--in Earth's atmosphere. Slated to launch aboard SpaceX's fourth commercial resupply mission to the space station, CATS was developed at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The data from this study will provide researchers with a more accurate idea of what kinds of particles exist in the atmosphere. This is important for understanding climate and weather, as well as how healthy the air is and if it is safe for things like airplane travel.

Researchers who have already claimed their space of the external real estate on the orbiting outpost will have until at least 2024 to collect data, depending on the lifespan of their project and equipment. With a decade ahead for additions to the collection for in-orbit research, the potential for discovery while hitching a ride attached to the space station will likely entice more researchers to join. Whether looking at Earth, the atmosphere or the universe beyond, instruments hosted by the space station stand to enrich knowledge in a wide array of disciplines to help extend exploration of this planet and beyond. In this way the space station shows what many of us already know--looking outside of ourselves is a good thing.

By Jessica Nimon
International Space Station Program Science Office
NASA's Johnson Space Center

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