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Journal of astronomical telescopes, instruments, and systems 8(01), 014007-1 (2022). doi:10.1117/1.JATIS.8.1.014007, The prototype Schwarzschild-Couder Telescope (pSCT) is a candidate for a medium-sized telescope in the Cherenkov Telescope Array. The pSCT is based on a novel dual mirror optics design which reduces the plate scale and allows for the use of silicon photomultipliers as photodetectors. The prototype pSCT camera currently has only the central sector instrumented with 25 camera modules (1600 pixels), providing a 2.68$^{\circ}$ field of view (FoV). The camera electronics are based on custom TARGET (TeV array readout with GSa/s sampling and event trigger) application specific integrated circuits. Field programmable gate arrays sample incoming signals at a gigasample per second. A single backplane provides camera-wide triggers. An upgrade of the pSCT camera is in progress, which will fully populate the focal plane. This will increase the number of pixels to 11,328, the number of backplanes to 9, and the FoV to 8.04$^{\circ}$. Here we give a detailed description of the pSCT camera, including the basic concept, mechanical design, detectors, electronics, current status and first light., Published by SPIE, [Bellingham, Wash.]

Data were obtained on stellar occultations by Neptune on June 7 and 25, 1985 in an attempt to validate previous data which supported the presence of a ring-like 'arc' near the planet. The data were taken with an IR photometer at the South African Astronomical Observatory using continuous measurements at 2.2 microns. One dip was observed in the light curve of an occulted binary star. The dip was similar to a previously observed dip and, because no dip was seen for the companion star, indicated a discontinuous structure. Two estimates, around 62,600 and 63,760 km, are made for the equatorial radius of the potential arc structure, which may be discontinuous on a scale of a few thousand kilometers.

The development, integration, and testing of the Energetic X‐ray Imaging Telescope Experiment (EXITE) are described. EXITE is a balloon‐borne hard x‐ray imaging payload with high sensitivity in the 20–300 keV band, angular resolution of 22 arcmin (with source locations to ∼2 arcmin) in a 3.4° FWHM field‐of‐view and energy resolution of 9% at 122 keV. Details of the detector system, a 34 cm diameter NaI scintillation crystal with image intensification and position‐sensitive readout, are described as well as the integration and testing of EXITE into a new balloon gondola with stable (∼1 arcmin) pointing. EXITE is able to carry out high‐sensitivity (∼10 mCrab) observations of SN 1987A to measure the Compton‐degraded x‐ray and gamma ray continuum, to search for the 122 keV cobalt‐57 line, and (at 0.1 msec time resolution) to search for the new pulsar thought to have been produced in the Sn 1987A event.