Instrument aboard Jupiter-bound spacecraft nails in-flight test

As European Space Agency (ESA)’s Jupiter Icy moons Explorer (Juice) spacecraft hurtled past the moon and Earth in mid-August to provide its first gravity assist maneuver to the Jovian system, the Southwest Research Institute-led Ultraviolet Spectrograph (UVS) instrument imaged the UV emissions radiating from the Earth and moon.

It was a successful test of one of three science instrument projects comprising NASA’s contribution to ESA’s Juice mission. The UVS data collected were then analyzed and found to be consistent with expectations for the moon and the Earth. This confirmation that the instrument works within specifications was not able to be fully achieved during pre-launch testing in a laboratory setting.

“This high-fidelity test confirmed what the instrument is supposed to do. We can now be confident that the data we will get from Jupiter’s moons will be just as accurate,” said SwRI’s Steven Persyn, Juice-UVS project manager (PM).

Weighing just over 40 pounds and drawing only 7.5 watts of power, UVS is smaller than a microwave oven, yet this powerful instrument will determine the relative concentrations of various elements and molecules in the atmospheres of Jupiter’s moons once in the Jovian system.

Aboard Juice, UVS will get close-up views of the Galilean moons Europa, Ganymede and Callisto, all thought to host liquid water beneath their icy surfaces. UVS will record ultraviolet light emitted, transmitted and reflected by these bodies, revealing the composition of their surfaces and tenuous atmospheres and how they interact with Jupiter and its giant magnetosphere. Additional scientific goals include observations of Jupiter itself as well as the gases from its volcanic moon Io that spread throughout the Jovian magnetosphere.

The Juice spacecraft is now on its way to Venus, where it will complete a gravity assist maneuver before heading back to Earth for another gravity assist to attain the momentum needed for its journey to the Jovian system.

The mission’s science goals focus on Jupiter and its system, making multiple flybys of the planet’s large, ocean-bearing satellites with a particular emphasis on investigating Ganymede as a potentially habitable planetary body. Being the only moon in the solar system known to have an internal magnetic field, Ganymede has auroral ovals like the northern and southern lights on Earth.

The UV emissions from Earth’s atmosphere observed during the recent gravity assists provide an especially good test of the plans for Juice-UVS to observe Ganymede’s UV aurora and other atmospheric features. It will also study the system as an archetype for gas giants in our solar system and beyond.

UVS is one of 10 science instruments and 11 investigations on the Juice spacecraft. As it begins an approximately 4.1-billion-mile (6.6-billion-kilometer), eight-year journey to the Jupiter system, the spacecraft has been busy deploying and activating its antennas, booms, sensors and instruments to check out and commission all its important subsystems. SwRI’s UVS instrument is the latest to succeed in this task.

A similar instrument, Europa-UVS, will travel aboard NASA’s Europa Clipper, which will take a more direct route to arrive at the Jupiter system 15 months before Juice and focus on studying the potential habitability of Europa.

“Our UVS instrument will complement the work that will be done by Europa-UVS allowing us to learn even more at the same time,” said SwRI’s Dr. Kurt Retherford, principal investigator (PI) of Europa-UVS and deputy PI for Juice-UVS. “Having both teams working with the UVS instruments based here at SwRI will make that coordination all the more efficient.”

The Juice spacecraft and science instruments were built by teams from 15 European countries, Japan and the United States. SwRI’s UVS instrument team includes additional scientists from the University of Colorado Boulder, the SETI institute, the University of Leicester (U.K.), Imperial College London (U.K.), the University of Liège (Belgium), the Royal Institute of Technology (Sweden) and the Laboratoire Atmosphères, Milieux, Observations Spatiales (France). The Planetary Missions Program Office at NASA’s Marshall Space Flight Center oversees the UVS contribution to ESA through the agency’s Solar System Exploration Program. The Juice spacecraft was developed by Airbus Defence and Space.