The objective of the proposed effort is to develop a 6U CubeSat instrument system capable of meeting the temperature and water vapor measurement requirements of the AIRS and CrIS instruments data products in the lower troposphere. The method employed will use a infrared grating spectromter with infrared detectors and micro-cryocooler. The measurement will be made in the 4-5 micron spectral region. This work is significant in that if selected, the CIRAS will demonstrate a critical science and meteorological measurement in a significantly smaller package enabling use in constellations for improved latency. The CIRAS can also be used as a gap filler in the event of a failure of the CrIS, and thereby providing insurance for the long-term data continuity of AIRS.