OMPS Limb Sensor II: Novel Operations to Fix Data Artifacts

Abstract:

The OMPS Limb sensor flying on the NPP-Suomi mission measures vertically-resolved limb spectral radiance profiles to derive a high spatial resolution ozone profile. The sensor uses both UV and visible light dispersed by a prism and imaged onto a single CCD to make profile measurements of the Earth limb radiance. The measurement challenges include a wide dynamic range in both spectral and spatial directions and demanding stray light requirements, especially for the UV wavelengths.

On NPP, the sensor uses two optical gains (bright and dim limb spectral images) and two integration times (Long and Short) to handle the dynamic range of the limb signal. The sensor also contains precisely-positioned spectral filters at the focal plane to control stray light. The multiple image approach creates noise in retrieved profiles at the bright-dim crossover points. The filters are challenging both in fabrication and in alignment.

The proposed operational change for the JPSS2 OMPS Limb sensor eliminates the multiple image approach and reduces stray light levels through use of different images for different wavelength channels. Through use of a stepped integration time scheme and on-board image consolidation, the spectral radiance measurements are improved and more pixels are available for downlink within the allotted data rate. We present the operational concept, results of ground testing using the Limb sensor engineering unit and estimates of expected on-orbit performance.