February 8, 2025 marks one year of UMBC's HARP2 instrument in space!

Wed, 12 Feb 2025 12:51:59 -0500
esi

The Hyper-Angular Rainbow Polarimeter (HARP2) is a multi-angle imaging polarimeter instrument, which was built, calibrated, and currently is supported by an interdisciplinary team of scientists and engineers at UMBC’s Earth and Space Institute (ESI). HARP2 was launched to space on-board the NASA Plankton Aerosol Cloud ocean Ecosystem (PACE) mission on February 8, 2024. The instrument was turned on over the next few days, and on February 19, 2024, ESI engineers began commissioning activities at NASA Goddard Space Flight Center (GSFC) to assess instrument health and validate its science operations.

On April 11, 2024, for the first time, the world saw what HARP2 sees from space: beautiful rainbows atop liquid water clouds, a hazy, blue atmosphere observed from oblique angles, aerosol plumes floating broadly over a dark ocean, and most importantly, wide swath imagery of the Earth, every two days. To date, HARP2 has imaged the entire Earth over 180 times and with special polarized eyes that reveal an almost alien world (see image below). Sensitivity to polarization allows scientists to discriminate different kinds, sizes, and shapes of aerosols (such as dust and smoke), separate liquid water droplets from ice crystals, and distinguish light scattering from molecules from information coming from the ocean. These measurements will help the climate community answer pressing science questions that could only be addressed with global data from a HARP-like instrument.

Photo: Global HARP2 data in top-of-atmosphere radiance, a form of energy, (top) and degree of linear polarization (DOLP, bottom), the ratio of polarized light to all light energy. The DOLP map emphasizes the direct reflection of the Sun off the ocean surface, the blue haze from light scattered by atmospheric molecules, and the "cloudbow", a ring-like signal that only comes from liquid water cloud droplets. (Credit: A. Puthukkudy/ESI)

HARP2 is an exciting leap in space technology and science capability for UMBC. The climate community is starting to use HARP2 data to benefit society and policy, to reduce our uncertainties in climate prediction, to study land use change, the interaction between aerosol particles and clouds, and the composition of phytoplankton in the ocean, and learning how to efficiently process the gigabytes and gigabytes of HARP2 data streaming down from PACE daily. Much of this work is led by scientists at the ESI along with our partners in GESTAR II and NASA GSFC.

Congratulations to UMBC, the Earth and Space Institute, and HARP2!