Vacuum System for Charge Management Device Testing at Precision Space Systems Laboratory

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Written in collaboration with Dr. Simon Barke of the Precision Space Systems Laboratory

The Precision Space Systems Laboratory (PSSL) at the University of Florida aims to develop instrumentation and measurement techniques for gravitational science and satellite navigation. In collaboration with the NASA Ames Research Center, the PSSL works on multiple missions for laser communication in space and measures the time difference between ground and space clocks.  However, the most significant project the PSSL is involved in is the Laser Interferometer Space Antenna (LISA), a mission to detect and measure gravitational waves from slow-moving astronomical sources by the European Space Agency (ESA) in partnership with NASA. 1

The spectrum of gravitational waves. European Space Agency

The measurement of gravitational waves can reveal information about the locations of binary stars, details about the properties of black holes, and even the collision and merger of galaxies, giving insight into our cosmic history. Recently, the PSSL hosted ANCORP engineering interns to discuss the lab’s role in the LISA mission and how their custom vacuum chamber system from ANCORP is helping achieve that goal.

LISA concept
Artist rendition of LISA system. University of Florida

The Laser Interferometer Space Antenna (LISA) system will comprise three spacecraft in a triangular formation separated by millions of kilometers and equipped with laser technology and sensors that will allow each spacecraft to detect minuscule changes in position relative to one another. The sensors on the spacecraft that record will be sensitive to distance fluctuations of just a few picometers. This data can then be translated into gravitational wave signals of certain amplitude, frequency, and direction of origin.  

However, to make measurements this precise, establishing a gravitational reference point is critical for the mission as position deflections caused by interferences such as noisy solar radiation would drown out the desired gravitational wave signals. The Precision Space Systems Laboratory has been awarded a NASA contract to complete a subsystem for the mission responsible for maintaining the gravitational reference for the sensors: the charge management device.2

The gravitational reference on board each spacecraft is a free-floating gold-platinum alloy test mass. The main measurement of distance fluctuations that allow for the detection of gravitational waves happen between those test masses. The charge management device in development at the University of Florida will utilize the photovoltaic effect through deep ultra-violet (DUV) light-emitting diodes (LEDs) to manage and influence the test mass electrical charge. Through this charge control, position changes of the test masses can effectively be attributed to gravitational effects alone, and it becomes possible to remove the influence of external environmental disturbances from the data for a clean gravitational wave signal.

ANCORP manufactured the custom cylindrical vacuum chamber, featured on the top of the page, outfitted with optical and electrical feedthroughs and viewports to support data collection, UV light transmission, and temperature control. The PSSL has been using the system for a couple of years, qualifying the DUV LEDs for space flight in a variety of precise tests under realistic conditions. Members of the lab proudly shared that the development and testing of any flight hardware for a mission is an incredible feat for a university lab. The Precision Space Systems lab is fortunate to work with their industrial partner, Fibertek, to qualify their technology for integration in the LISA mission.

Custom ANCORP chamber system created for PSSL. Stefan Marinak (ANCORP)
By adequately testing and developing the DUV LED system and their hermetically sealed packaging for charge management, the team will be able to propose them as an alternative to mercury lamps for charge management.
DUV LED lights must provide substantial benefits to challenge the flight heritage and high-power capabilities of mercury lamps for charge management. Luckily for the PSSL, the benefits of using DUV LEDs over mercury lamps are numerous and include “being lighter, the potential for pulsing, and increased control for better manipulation of the test mass,” explained Dr. Simon Barke.
This mission set forth by the ESA still has many years to go, with a launch expected in the mid-2030s.3 Though that is some time away, ANCORP looks forward to monitoring the development of the mission and is immensely proud that our manufacturing capabilities have empowered the development of one of the mission’s subsystems.

Do you have a project or application requiring the custom development of a high to ultra-high vacuum chamber? Request a quote from ANCORP’s team of engineers today! 

1 Precision Space Systems Laboratory, https://pssl.mae.ufl.edu/#home/main/

2 Laser Interferometer Space Antenna, ESA, NASA, https://lisa.nasa.gov/

3 LISA mission moves to final design phase, The European Space Agency, https://www.esa.int/Science_Exploration/Space_Science/LISA_mission_moves_to_final_design_phase

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