At DTU, an instrument is taking shape. It's called juLIET and is not very big; the prototype looks like something you can easily carry in your hands. The instrument is being designed and built by Katcha Koch Winther and her colleagues at DTU Space as part of her PhD project, and if everything goes according to plan, the instrument will be mounted in the ROMEO satellite, set to be launched into space in 2026. Here, juLIET will take pictures of the Moon. Or rather: It should take pictures of earthshine.
"Down here on Earth, we know about moonshine, which is the sunlight that the moon reflects. Conversely, earthshine is the light reflected by the Earth and falling on the Moon," explains Katcha Koch Winther.
Using the juLIET instrument to take photos of the earthshine will enable us to measure how much light the Earth reflects. This allows climate researchers to follow the development of the Earth's energy balance more closely. That balance refers to the relationship between the energy that the Earth receives from the Sun and the energy that the Earth sends back to space. This balance is crucial for understanding the climate and weather phenomena, says Peter Thejll, climate researcher at DMI, who is among the researchers who will use the juLIET measurements.
"The sun is our primary source of energy on Earth and therefore plays a crucial role in the planet's energy balance and thus our climate. But not all sunlight is included in the energy balance, because some of it hits clouds, deserts, polar ice caps, and mountain range glaciers, which are surfaces that are excellent at reflecting sunlight and sending it back into space," explains Peter Thejll.
