Stratospheric aerosols can have large effects on both the radiative balance of the planet and atmospheric composition. In this region of the atmosphere, aerosols are predominantly sulfate, much of them volcanic in origin. Analogously, explosive pyrocumulonimbus (pyroCb) convection from extreme midlatitude and boreal forest fire events can directly inject aerosols into the stratosphere. After injection, volcanic and pyroCb aerosols can persist for many months in the stratosphere; however, the overall contribution of pyroCb events to the stratospheric aerosol budget and effects on the broader Earth system remain uncertain.

Vertical profiles of stratospheric aerosols and clouds (at altitudes ranging from 12-30 km) from airborne lidars are desired to study their influence on the climate system, as aircraft can target these plumes and take repeated measurements to observe the evolution of the plume properties. However, most airborne lidar systems point nadir and the highest-flying NASA aircraft, the NASA ER-2, only flights at 20 km. The only nadir and zenith pointing lidar instrument to meet this science need is Roscoe. Previous flights aboard the ER-2 and WB-57 have demonstrated the ability of Roscoe to provide direct measurements of plume altitudes and cloud heights. However, the performance of the instrument is impeded by thermally induced distortions of the optical bench causing misalignment in flight.

Analysis shows that the key issue with the Roscoe instrument is the aluminum transceiver optical bench. A new transceiver optical bench made of titanium has been procured which will reduce the thermally induced movements on the optical bench by a factor of three and should allow the transceiver boresight to remain aligned. This IRAD is to fund the labor efforts and small parts needed for replacing the current aluminum transceiver optical bench with the new titanium transceiver optical bench as well as investigating polarization issues seen in the data.

In one of NASA's newest EVS missions, called the Pyrocumulonimbus Experiment (PYREX) (led by NRL), researchers will investigate the conditions that lead to the formation of pyroCb. PIREX plans to fly the NASA ER-2 and WB-57, equipped with a lidar instrument, over the western U.S. and Canada. It is essential to perform this work now so that Roscoe can be ready to fly in PYREX and to demonstrate the science capabilities of the Roscoe instrument during NASA ER-2 flights in January 2025 out of southern California for ICESat-2 and EarthCARE validation.