Algorithm science to operations for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) visible/infrared imager/radiometer suite (VIIRS)
The VIIRS sensor provides measurements for 22 environmental data records (EDRs) addressing the atmosphere, ocean surface temperature, ocean color, land parameters, aerosols, imaging for clouds and ice, and more. That is, the VIIRS collects visible and infrared radiometric data of the Earth's atmosphere, ocean, and land surfaces. Data types include atmospheric, clouds, Earth radiation budget, land/water and sea surface temperature, ocean color, and low light imagery. This wide scope of measurements calls for the preparation of a multiplicity of algorithm theoretical basis documents (ATBDs), and, additionally, for intermediate products such as cloud mask, et al. Furthermore, the VIIRS interacts with three or more other sensors. This paper addresses selected and crucial elements of the process being used to convert and test an immense volume of a maturing and changing science code to the initial operational source code in preparation for launch of NPP. The integrity of the original science code is maintained and enhanced via baseline comparisons when re-hosted, in addition to multiple planned code performance reviews.
Ozone Profile Retrieval from an Advanced Infrared Sounder: Experiments with Tropopause-Based Climatology and Optimal Estimation Approach
Abstract Motivated by a significant potential for retrieving atmospheric ozone profile information from advanced satellite infrared sounders, this study investigates various methods to optimize ozone retrievals. A set of retrieval experiments has been performed to assess the impact of different background states (or the a priori states) and retrieval algorithms on the retrieved ozone profiles in the upper troposphere and lower stratosphere (UTLS) using Atmospheric Infrared Sounder (AIRS) measurements. A new tropopause-based ozone climatology, using publicly available global ozonesonde data to construct the a priori state, is described. Comparisons are made with the AIRS version 5 (v5) ozone climatology. The authors also present the result of a newly implemented optimal estimation (OE) algorithm and compare it to the current AIRS science team (AST) algorithm used in version 5. The ozone climatology using tropopause-referenced coordinates better preserves the shape and the magnitude of the ozone gradient ac...
End-to-end performance assessment of the National Polar-orbiting Operational Environmental Satellite System environmental data records
The tri-agency Integrated Program Office (IPO) is managing the development of the National Polar-orbiting Operational Environmental Satellite System (NPOESS). Later this decade, the IPO, through its prime contractor, Northrop Grumman Space Technology (NGST), will launch NPOESS spacecraft into three orbital planes (1330, 1730, and 2130 equatorial ascending nodal crossing times) to provide global coverage with a data refresh rate of approximately four hours. A globally distributed ground system will deliver 95 percent of the data within 26 minutes from the time of on-orbit collection. With the development of NPOESS, we are evolving the existing “weather” satellites into integrated environmental observing systems. To meet user-validated requirements, NPOESS will deliver global data for 55 Environmental Data Records (EDRs). Performance characteristics and attributes have been defined for each of the 55 parameters, including: horizontal/vertical resolution; mapping accuracy; measurement range; measurement precision and uncertainty; refresh rate; data latency; and geographic coverage. Long-term stability requirements have been defined for key parameters to ensure temporal consistency and continuity of data over the operational life of NPOESS. The actual EDR performances will be a result of the sensor and algorithm performances. In order for NPOESS program to determine estimates of EDR performance based on current design data and to assess potential sensor design changes or algorithm modifications, NGST developed an Integrated Weather Products Test Bed (IWPTB). This system can generate simulated radiances from mission/orbit variable, sensor variables, atmospheric and background conditions, and radiative transfer models. These simulated radiances at aperture are used with sensor models and spacecraft factors to generate simulated radiometric temperatures which are processed by science retrieval code to generate EDRs. This paper presents an assessment of the impact of the VIIRS sensor design modification to correct Modulated Instrument Background in the sensor’s optical train. This assessment, which focuses on the Sea Surface Temperature EDR in particular, was generated by the IWPTB end-to-end performance assessment capability.