Cloud Imaging and Particle Size Experiment (CIPS)
The Cloud Imaging and Particle Size (CIPS) Experiment is a nadir-viewing ultra-violet (UV) imager that has been in operation since 2007 aboard the NASA Aeronomy of Ice in the Mesosphere (AIM) satellite that provides unprecedented global measurements of polar mesospheric clouds (PMC). The overall goal of the AIM mission is to resolve why PMC's form and why they vary. CIPS measures scattered solar radiation at 265 nm using a unique four-camera design to obtain near-simultaneous measurements of the single-scattering albedo of PMCs from multiple view angles. Using this technique it is possible to directly measure the ice particle scattering phase function, from which one can retrieve several fundamental parameters related to the cloud microphysics – albedo, particle mean radius, and ice water content.
The CIPS instrument was designed and built by the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP), which is responsible for CIPS data processing and provides mission operations for the AIM satellite. CPI’s Boulder office supports LASP in numerous key areas of CIPS data processing, including development, testing and implementation of cloud detection and geophysical retrieval algorithms; enhancement of core data processing software; documentation; validation; characterization; and error analysis for all CIPS data products.
CPI has helped LASP evaluate the CIPS data processing system, with particular emphasis on improving the Level 2 retrieval algorithms. CPI personnel have performed extensive characterization and evaluation studies on the CIPS data products, and in the process have rewritten or improved much of the algorithms and production software used to generate CIPS Level 1-3 data.
Level 1A Processing
CPI has developed entirely new algorithms for implementing key steps in the Level 1A calibration, including camera flat-fielding and camera-to-camera signal normalization. The flat-field corrections measured in the lab pre-launch are insufficient to accurately characterize the CIPS cameras in-flight. CPI developed new algorithms that derive time-dependent flat field calibration using multiple sources of in-flight calibration images. These algorithms have been implemented operationally.
Level 2 Processing
Level 2 retrievals are the primary CIPS geophysical data product. CPI has led an effort in which the level 2 processing codes have been entirely rewritten to produce a new operational data set – Version 4.20 - which represents a significant improvement over previous CIPS data versions. The V4.20 level 2 algorithms have been rigorously tested and evaluated by CPI, and integrated into the CIPS operational data processing architecture. The figure below shows a sample V4.20 cloud albedo image for a single orbit. This image illustrates the richness of detail available in the V4.20 data set, which is produced at approximately 10 times higher resolution than the previous V3.20 data.
Level 3 Processing
CPI has led an effort to develop two new, higher-level data products used extensively by CIPS data users for scientific analysis. The Level 3C product is a full-season file containing orbit-by-orbit cloud parameter data (and associated meta-data) binned in 1-degree latitude bins. The Level 3D data product is also a full-season file that provides a subset of the CIPS Level 2 retrievals in the AIM common volume region (CIPS pixels overlapping the line-of-sight sampling of SOFIE, a solar occultation instrument co-manifested on the AIM satellite). CPI has developed, tested and implemented the algorithms for producing these data products operationally.