2 external instruments installed on ISS over New Year's holiday

An artist's rendering of the Space Debris Senor installed on the International Space Station. It was one of two external instruments recently installed at the orbiting outpost. Credit: NASA

While many around the world celebrated the arrival of 2018 with champagne, fireworks and social gatherings, robotics operators at NASA’s Johnson Space Center rang in the New Year by working to remotely install new external instruments recently brought to International Space Station inside the trunk of SpaceX’s CRS-13 Dragon cargo spacecraft.

On Dec. 28, 2017, robotic operators worked to extract the first of two external instruments from Dragon’s trunk: the Total and Spectral Solar Irradiance Sensor, or TSIS-1 for short.

TSIS-1 was developed by the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder, Colorado. It is designed to measure total solar irradiance and solar spectral irradiance. According to NASA, the former will help establish Earth’s total energy input while the latter will contribute to the understanding of how the atmosphere responds to solar output changes.

The instrument is 363 kilograms and has dimensions 1.2 meters by 1.2 meters by 2.4 meters. During transport, it was compacted to a 1.2-meter cube. However, according to NASA, it transforms to nearly twice that once installed on the space station.

Over five years, the instrument will monitor solar energy over various wavelengths and provide the most accurate measurements of sunlight.

Extraction took place over many hours using the 17.6-meter robotic Canadarm2 with the smaller Dextre robotic “hand” attached. The instrument was installed on ExPRESS Logistics Carrier 3 (itself located on the P3 truss segment) at position 5.

Actual installation of TSIS-1 took place on Dec. 30, 2017, with the deployment of the instrument taking place on New Year’s Eve.

The next task for Earth-based robotics teams was to extract the second of the two external instruments from Dragon’s trunk: the Space Debris Sensor. That took place over New Year’s Day.

SDS’s goal is to monitor impacts caused by small-scale debris over a two-to-three-year period. It has a three-layer sensor that can record the time and scale of impacts. The goal is to be able to estimate the amount of debris smaller than one millimeter that exists in low-Earth orbit.

“Debris this small has the potential to damage exposed thermal protection systems, spacesuits, windows and unshielded sensitive equipment,” said Joseph Hamilton, the project’s principal investigator, in a Dec. 12 news release by NASA. “On the space station, it can create sharp edges on handholds along the path of spacewalkers, which can also cause damage to the suits.”

There are currently more than 20,000 pieces of debris tracked in space that are larger than several inches. NASA says the vast majority of space junk is too small to be tracked by ground-based sensors. The U.S. space agency estimates that there is more than 100 million tiny pieces of debris less than one centimeter in Earth's orbit. 

According to NASA, this information will also allow for a new set of sensors to be developed and placed in other orbits beyond the station's. Ultimately, this information will be used to improve debris detection, and develop the technology needed to protect both satellites and human spaceflight missions.

Once removed from Dragon’s trunk via Dextre and Canadarm2, SDS was placed on one of the four external racks on the European Columbus module.

With Dragon’s trunk emptied, robotic operators commanded Dextre and Canadarm2 to remove RapidScat (also located on Columbus), which was a space-based instrument used to measure Earthly wind speeds.

RapidScat was launched in September 2014 aboard SpaceX’s CRS-4 Dragon. While the mission was considered successful, on Aug. 19, 2016, a power distribution unit failure occurred forcing the resource-reliant instrument to shut down. NASA was unable to restore the instrument and terminated operations several months later on Nov. 28, 2016.

With RapidScat’s removal, it frees up a spot on the Columbus module’s payload truss for future external instruments.

Canadarm2, with Dextre, placed RapidScat inside Dragon’s trunk where it will remain until the spacecraft is unberthed and the trunk jettisoned following the capsule’s reentry burn. That is expected to occur on Jan. 13, 2018.

The trunk, with RapidScat inside, will burn up upon reentry while the heat shield-protected capsule with finished experiments and other items in need of a return to Earth will splash down in the Pacific Ocean off the coast of Baja California. SpaceX teams are expected to recover the capsule shortly after splashdown.

NOTE: While this article was written by Derek Richardson, it was originally published at SpaceFlight Insider. Feel free to head over there to read all the stuff they write about!