Join our researchers as they install their instrument on NASA’s IMAP spacecraft, set to launch next year on a mission to study the solar wind.

The Interstellar Mapping and Acceleration Probe (IMAP) spacecraft will observe and map the Sun’s heliosphere – the volume of space filled with particles streaming out from the Sun, known as the solar wind – and study how it interacts with the local galactic neighbourhood beyond, known as the interstellar medium. 

Everything is in its ‘final flight configuration’. We won’t unplug it again. Professor Tim Horbury

Imperial physicists have built a magnetometer (MAG) instrument for the mission, which will measure the interplanetary magnetic field around the spacecraft. From these measurements, MAG will identify interplanetary shocks and measure the waves and turbulence that scatter particles in the solar wind.

The UK Space Agency has supported the UK development of the IMAP mission with £4.2 million, including funding for the MAG instrument.

IMAP is now being assembled at the Johns Hopkins University Applied Physics Lab (APL) in Maryland, USA, before launch in summer 2025. MAG’s Principal Investigator Professor Tim Horbury and Instrument Manager Helen O’Brien went out to APL in August to help MAG get installed on the spacecraft.

Here, Professor Horbury talks us through some of the photos and videos that captured the excitement of seeing their instrument get into its final position – ready for space.

All images credit NASA/Johns Hopkins/Princeton/Ed Whitman.

“It feels very real when you’re in a room with it. The sensors were mounted on a boom – a long arm that will keep them away from the spacecraft when it’s in space, but for now is folded onto the main craft. So the sensors are mounted and we’ve plugged them in, along with the electronics box, so everything is in its ‘final flight configuration’. We won’t unplug it again.”

“In our South Kensington lab, the sensors were always in special ‘cans’ when switched on, to shield them from the Earth’s magnetic field. Now, whenever they are switched on – which will be at various times in the next few months – they will measure the Earth’s and the spacecraft’s magnetic fields.”

“Many of these times will be when the spacecraft goes through several rigorous tests to check everything will survive launch and the space environment, including thermal, vibration, electromagnetic and acoustic shocks.”

“We also tested the boom deployment. To simulate the lack of gravity, the spacecraft was turned on its side and the boom suspended by ropes. It was then ‘led’ out by an engineer. The moment the boom is released, there is a loud ‘pop’ that’s a little disconcerting, but everything worked as it should.”

 ^{Video credit: NASA/Johns Hopkins/Princeton/Lee Hobson}

“We also saw the spacecraft spin many times. In space, this is necessary to keep it stable and to ensure the particle sensors onboard get a full view of the sky. It also helps to calibrate the MAG sensors.”

^{Video credit: NASA/Johns Hopkins/Princeton}

“Before the boom is deployed, one of the MAG sensors will sit among the solar panels. As these will constantly face the Sun when out in space, the sensor could get extremely hot in its first few days.

“Ideally, we want to turn the sensors on to measure the magnetic field before and after the boom unfolds, to compare them, but if they’re too hot we can’t risk it. Once the spacecraft launches from Cape Canaveral in Florida, we’re going straight to an operations centre in Colorado to measure the temperatures and make that decision.”

“The team at APL have been outstanding. It’s an extraordinary operation, a complete juggling act, but they do it while allowing for setbacks that mean the overall project runs very smoothly.”

Princeton University professor David J. McComas leads the IMAP mission with an international team of 25 partner institutions. The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland builds the spacecraft and operates the mission. IMAP is the fifth mission in NASA’s Solar Terrestrial Probes (STP) program portfolio. The Explorers and Heliophysics Project Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the STP Program for the agency’s Heliophysics Division of NASA’s Science Mission Directorate.