NASA CTIM ‘first light’ data outshines expectations for solar irradiance measurements

CTIM is the smallest instrument ever dispatched to study total solar irradiance. Credits: University of Colorado, Boulder

First light data from NASA’s Compact Total Irradiance Monitor (CTIM) will soon be publicly available, paving the way for new insights into Earth’s relationship with total solar irradiance.

Dave Harber, Principal Investigator for CTIM and Instrument Engineer at the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP), presented this data at the American Meteorological Society’s 2023 annual meeting.

“Perhaps the most surprising result so far is the stability of the detectors. We have not observed any statistically significant degradation of the primary detectors yet over 250 hours of direct unfiltered solar exposure,” said Harber.

This initial data set includes solar and deep-space measurements collected during twelve orbits around the world. It’s is a promising start for a technology validation mission that could help researchers better understand severe weather, climate change, and other global forces.

CTIM, which launched July 2022, is the smallest instrument ever dispatched to study total solar irradiance and will help scientists determine if small satellites could be as effective at measuring total solar irradiance as larger instruments like the Total Irradiance Monitor (TIM).

“Although the first light dataset was relatively short, we’ve used subsequent on-orbit measurements taken over the following four months to refine temperature corrections and the deep-space model used to analyze those measurements,” said Harber.

CTIM features a unique, ultra-black bolometer made of vertically aligned carbon nanotubes, which Harber and his team developed alongside colleagues from the National Institute of Standards and Technology. Though Harber expected the material to perform well, he was surprised by just how effective CTIM’s detectors proved to be even in the rigors of space.

“From lab testing we did expect the vertically aligned carbon nanotube optical absorber to be quite stable, but the on-orbit performance to this point has exceeded our expectations,” said Harber.

CTIM’s mission will last a little over two years. During that time, Harber and his team will continue gathering total solar irradiance measurements and honing their instrument design.

NASA, along with the White House and other federal agencies, has designated 2023 as the Year of Open Science. Harber plans on publishing his CTIM data in February, and it will be available to the public here.