The EarthCARE broadband radiometer detectors

Abstract

The Broadband Radiometer (BBR) is an instrument being developed for the ESA EarthCARE satellite. The BBR instrument objective is to provide top-of-atmosphere (TOA) radiance measurements in two spectral channels, and over three along-track directions. The instrument has three fixed telescopes (one for each view) each containing a broadband detector. Each detector consists of an uncooled 30-pixel linear focal plane array (FPA) coated with gold black in order to ensure uniform spectral responsivity from 0.2 µm to 50 µm. The FPA is hybridized with a readout integrated circuit (ROIC) and a proximity electronics circuit-card assembly (CCA) packaged in an aluminum base plate with cover. This paper provides a technical description of the detector design and operation. Performance data at the FPA pixel level as well as unit-level test results on early prototypes of the detectors are also presented.

On the figure of merit of uncooled bolometers fabricated at INO

“…INO has been active in the development of customized uncooled bolometers for more than 20 years [1][2][3][4][5][6] . Various applications were targeted, including space applications where linear and 2D arrays were fabricated for Earth observation [3][4][5] .…”

“…Various applications were targeted, including space applications where linear and 2D arrays were fabricated for Earth observation [3][4][5] . Although INO's detector technology was significantly improved over the years 7,8 , its benchmarking has long been hindered by the unavailability of high quality ReadOut Integrated Circuits (ROIC) compatible with commercial needs.…”

Vanadium oxide thin film with improved sheet resistance uniformity

“…Numerous custom uncooled Focal Plan Arrays (FPAs) have been developed for both space and commercial applications. Examples of prototypes that were developed include 128x128 (52 µm) 1 , 160x120 (52 µm) 2 , 256x1 (52 µm) 3 , 512x3 (39 µm) 4 , EarthCARE BBR (100 µm) 5 and 384x288 (35 µm) 6 arrays. More recently INO has, in the course of the ESA's GSTP5 program, developed 17 µm bolometers for a megapixel array (see Figure 1).…”

Performance characterization of the EarthCARE BBR Detectors

“…The FPA is based on INO's VO x microbolometer technology while the ROIC used is the XRO3501 by XenICs. The FPA is a linear array of 30 microbolometer pixels on a 100-µm pitch, specially designed and fabricated for the BBR instrument [3]. The linear array is matched by an array of unsuspended (shunt) pixels such that each pair of pixels corresponds to a resistance half-bridge, which middle point is fed into the ROIC integrator input.…”

“…The FPA linear array is covered with a gold black absorber in order to achieve the spectral uniformity required. The gold black layer is subsequently trimmed by laser micromachining to ensure individual pixel definition with a fill factor of at least 90% [3].…”