Recent field campaigns with CERES instruments

Abstract

Abstract – Clouds and the Earth’s Radiant Energy Sy stem instruments (scanners) on board the Terra and Aqua satellites have been used to meet variety of science data collection goals since their launch. Using a special programmable azimuth plan scan (PAPS) mode, a scanner collects radiation measurements of specified Earth targets or of a prescribed spatial orientation. Ongoing investigation of instruments’ consistency has put some restrictions on scanning directions, partially alleviated by introducing a new elevation profile. Main objective of th is paper is to explain scanning ca pabilities of the instruments under new conditions, and illustrate them with five different field campaigns of 2006. I. INTRODUCTION A Clouds and the Earth’s Radiant Energy System (CERES) instrument is a scanning thermistor bolometer designed to measure reflected solar radiation and outgoing longwave radiation from the Earth for radiation budget studies [1]. CERES instruments have played an important role in the Earth observing mission on board the TRMM, Terra and Aqua satellites. Their science data have been an invaluable addition to the two-decade long Earth’s radiation budget data set [2]. Remaining CERES instruments, FM1, FM2, and FM3, have been operating on board the Terra and Aqua satellites for six years, and for 4 years, respectively. Terra and Aqua satellites are in sun-synchronous, polar orbits with equatorial crossings at 10:30AM (descending) and 1:30PM (ascending), respectively. This constellation offers a rare opportunity to provide almost simultaneous ob servations of Earth targets near the orbital nodes in the Northern and Southern Hemispheres. CERES instruments have been used in various field campaigns to provide increased coverage of selected areas to meet research goals [3, 4]. In all thes e campaigns, scanners were put in a pr ogrammable azimuth plan scan (PAPS) mode to observe targeted areas from any direction. However, an ongoing investigation of instruments’ degradation and inconsistency has put restrictions on scanning directions, and effectively eliminated any forward sweep of a scanner. This paper explains CERES operations under new restrictions, and presents field campaigns with CERES participation in 2006. The included are: (a) FM1-FM3 validation campaign, (b) FM2-GERB1 validation campaign, (c) AMMA or African Monsoon Multidisciplinary Analysis campaign, (d) SCALES, or a GERB ground validation campaign at the Valencia Anchor Station, and also (e) true along-track scan mode. II. CERES OPERATIONS A CERES scanner has three channels: total (0.3-100 P m), shortwave (0.3-5 P m), and a longwave window (8-12 P m) which measure different parts of the spectrum. A full sweep lasts 6.6 sec., and with a sampling rate of 100sec