Development of detectors for space missions and balloon flights

Abstract

We are developing compact astronomical payloads for ultraviolet (UV) observations from CubeSats and high altitude balloons. It is important to have a highly sensitive, low noise detector in the UV region where the incoming photons are very few. Micro Channel Plate (MCP) based photon counting detectors are widely used in UV astronomy due to their low noise levels, high sensitivity, and large area. The rst part of the thesis describes the design, fabrication, and characterization of a photon counting, intensi ed CMOS (iCMOS) detector. The detector consists of a Z-stack, 40 mm MCP from Photek with an S20 photocathode and a phosphor screen anode. The readout system uses o -the-shelf components for the focusing optics, image sensor, and backend electronics. The heart of the electronics is a Field Programmable Gate Array (FPGA) board that controls the input signals from the CMOS and interfaces the output data to storage and telemetry. The FPGA performs real-time data processing as well, including the identi cation of actual photon events and their centroiding with sub-pixel accuracy. The detector is being used as the back end instrument of two of our UV payloads on a balloon platform above 40 km. One of the instruments is berfed, near UV spectrograph for atmospheric observations in the 250 { 400 nm region. The detector also ies on a wide- eld UV imager for observing solar system objects such as comets and asteroids and other bright UV transients. It is an all-refractive 70 mm telescope in the 250 { 350 nm wavelength range with a 10:8 eld of view. One of the space- ight opportunities for the detector is the PESIT-IIA Observatory for the Night Sky (PIONS), a near UV imaging telescope to be own on a small satellite. The major scienti c goals are to detect and characterize transients such as massive star explosions, stellar ares, and tidal disruption events. The camera has a 150 mm primary aperture with a 3 eld of view and images the sky in the 180 { 280 nm region with a 1300 resolution. We can observe targets as faint as 21st magnitude in a 1200 seconds exposure. We are also working on far UV instruments and detectors, by assembling a bare MCP with a custom-coated, semi-transparent photocathode. The photocathode is fabricated by thin lm deposition of CsI crystals on an MgF2 window. I will also brie y describe the future work on the design and fabrication of an FUV imaging spectrograph and associated technologies.