Improvements to the ACATS Lidar and Development of a NASA Field Campaign Concept

Vertical profile measurements of clouds and aerosols (dust, smoke, man-made pollution) from laser remote sensing instruments, such as the Airborne Cloud-Aerosol Transport System (ACATS) managed at NASA Goddard Space Flight Center (GSFC), are desired to study the interaction of clouds and aerosols and their influence on the climate system. This project consists of the installation of a new ACATS calibration device and mechanical modifications to the ACATS receiver subsystem. These modifications will result in more accurate measurements from the instrument. In addition, this project includes preparations for GSFC-lead field campaign to study the influence of aerosols on clouds and radiaiton that will include ACATS as a payload on a NASA aircraft.

Clouds and aerosols can have numerous effects on the atmospheric radiation budget. Ice clouds cause a warming effect, while water clouds can result in a cooling effect. During cloud-free conditions, aerosols such as desert dust and smoke from biomass burning can induce a change in radiative forcing at a magnitude comparable to that of greenhouse gases but opposite the sign. Additionally, aerosol can interact with clouds, changing the radiative effects on the atmosphere. These cloud and aerosol effects on the atmospheric radiation budget remain a major uncertainty in understanding and predicting the climate system.

Direct measurements of extinction vertical profiles from high spectral resolution lidars (HSRLs), such as the Airborne Cloud-Aerosol Transport System (ACATS) managed at NASA Goddard Space Flight Center (GSFC), are desired to study the interaction of clouds and aerosols and their influence on the climate system. Previous flights aboard a NASA high-altitude aircraft have demonstrated the ability of ACATS to provide direct measurements of extinction for short flight segments. However, the performance of the instrument is impeded by poor instrument calibration. This project includes modifications to the receiver subsystem that enable implementation and testing of a calibration device for improved results.

This project also supports the development of a field campaign to study the influence of aerosols on clouds and radiation. The field campaign will include the ACATS instrument and several other earth science instruments that fly on NASA aircrafts, as well as a management team that primarily consists of NASA and NOAA personnel.

The objectives of this project are as follows:

1. Improve the ACATS instrument calibration and overall functionality of the receiver subsystem.
2. Ensure the ACATS instrument is ready for future flights on NASA aircraft.
3. Develop the science goals and aircraft configurations for the field campaign proposal that includes the ACATS instrument and several other earth science instruments.

The overall goal of this project is to have ACATS ready to participate in future field campaigns and develop the field campaign concept that will include ACATS. The tasks that will be completed to achieve the objectives of project are as follows:

1. Integrate and test the new calibration device (filters, diffusers, and servo actuator assemblies) with the current receiver optics (Objective #1).
2. Oversee the design and installation of a new receiver enclosure that is both durable and meets thermal and mechanical requirements (Objective #1).
3. Test the modified system both in the lab at GSFC and on a NASA aircraft (Objective #2).
4. Develop the science goals and aircraft configurations for the field campaign proposal (Objective #3).