Gold black is made by evaporating gold in a nitrogen atmosphere, resulting in a film that has nearly perfect absorption properties.
How Clouds Control Climate
Studying the radiant energy from objects such as clouds in Earth’s atmosphere can tell us a lot about their behavior and interaction with larger weather systems. JPL has successfully built and flight-qualified the focal plane module (FPM) for the Radiation Budget Instrument (RBI), which was to be a NASA climate experiment that measures the effect of clouds on Earth’s energy balance.
Specific custom thermopile chips were designed and fabricated in MDL for RBI. These chips would be a key enabling technology for the entire RBI mission and JPL would deliver six flight-qualified FPMs. The FPMs met all the performance and environmental requirements for RBI including a response time of 8 ms and a noise equivalent power (NEP) of 1 nW —a factor of seven times lower than the previous instrument Clouds and Earth’s Radiant Energy System (CERES). RBI was designed as a passive remote-sensing instrument as the follow-on instrument to CERES to measure our planet’s short- and longwave radiation budget. The focal plane arrays were micromachined at the MDL and then integrated into subassembly modules to be mounted on the optical telescope of the instrument.
The MDL FPM is composed of a thermopile detector array, a rigid-flex board, and a focal plane block. Thermopile detectors are widely used in applications that require accurate radiometry without the need to cool the instrument below room temperature. Such imagers do not require electrical bias, and generate a voltage output that is proportional to the input radiation signal. They have negligible 1/f noise and they are well suited for broadband and spectral radiometers for Earth and space science applications.
The signal from the thermopile array is amplified by a flight-qualified commercial op-amp. The calibration scheme of the instrument was designed to have the RBI FPM periodically focus on a visible calibration, a solar calibration, and an infrared calibration target, to allow it to conduct onboard temperature calibrations. The FPM is customized to meet all the requirements of the previous instrument while substantially improving the performance of the RBI.
To make the detectors absorb light from the ultraviolet to the far-infrared, a specialized deposition tool is used to grow “gold black” on the detector’s absorber.
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The RBI focal plane module (FPM) that JPL delivered to Harris Corporation in spring 2017.
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