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12m Radio Telescope
Room temperature receivers
The Arecibo Observatory (AO) operates a 12-m diameter parabolic reflector antenna. It is an alt-azimuth mount telescope with primary focal length to diameter ratio of 0.375. It is fully steerable covering an elevation range 10o - 88o. The telescope is equipped with room temperature, dual polarized receivers operating near 2.21–2.34 GHz (S-band) and 8.1–9.2 GHz (X band). The antenna was commissioned in 2011, but was not regularly used for astronomy observations. During 2021, the AO engineering team (Phil Perillat, Felix Fernandez, Luis Quintero and the technical staff) integrated the receiver system with Mock Spectrometer and VLBI backend and successfully commissioned the system for astronomy observations by December 2021 (see Fig. 1). Regular solar observations using the X-band system were started on 18 December 2021 (see Fig. 2). The S-band system was released for observations by the end of March 2022, which is now being used for Pulsar and Solar observations.
Figure 1: (Left) Recombination lines observed toward Orion A at frequencies near 8.5 GHz with the 12m telescope (spectrum by Anna McGilvray and Anish Roshi). Three alpha transitions were observed simultaneously with three Mock spectrometers. The spectrum shown is the average of the 3 alpha transitions. Both hydrogen and helium lines were clearly detected. The H113β line was present in one of the spectral bands, which is seen in the average spectrum near -220 km/s. (Right) Average pulse profile of the Vela pulsar observed near 8.7 GHz with the 12m telescope (profile by Ben Perera). The observations used 7 Mock spectrometers configured in pulsar mode spanning a frequency range of about 1 GHz over 5 minutes.
Figure 2: Arecibo 12m telescope image of Sun at 8.647 GHz (on the left) compared with SDO EUV (wavelength 19.3 nm) image (on the right). Angular resolution of the 8.6 GHz image is about 10 arcmin. Starting from mid December 2021, AO recorded "east-west" scans of the Sun using the X-band receiver of the 12m telescope and moving in steps of ~5 arcmin covering a declination range between -1 and +1 degree with respect to the center declination of the Sun. These images are obtained from the February 2022 scans. (P. K. Manoharan and Phil Perillat).
Instruments Under Development
Wideband (2.3 – 14 GHz), Cryogenic Front-end for the 12m telescope
The poor system performance and relatively narrow bandwidth of the room temperature receivers of the 12m telescope are not widely useful for radio astronomy observations. Therefore we are upgrading the current receiver system with a wideband (2.3 – 14 GHz), cryogenic frontend. The expected system temperature is about 35 K over the full bandwidth. This upgrade will enable novel radio astronomy projects that range from tracking inhomogeneities in the solar wind, illuminating the underlying physics of pulsars and searching for FRB and sensitive spectral line observations of the galactic plane (see the list below). The cryogenic system is fully funded by the National Science Foundation. The system will be built by CryoElec LLC, Arizona and the work will start in April 2022. Science cases The main science drivers for the 12-m antenna include, but not limited to: Very Long Baseline Interferometer (VLBI) observations with the European VLBI network. As a single-dish it is extremely useful to monitor interplanetary scintillation of selected compact radio sources and to track coronal mass ejections between the near-Sun region to inner heliosphere. Predict the arrival of space weather events at the Earth’s magnetosphere. High-cadence, regular monitoring of bright young pulsars and millisecond pulsars, as well as magnetars. Followup observations over a broad frequency range of energetic repeating FRBs, extragalactic supernova events, and gamma ray bursts. Galactic plane survey of CH and prebiotic molecular lines. Monitoring flux density variability of extragalactic sources. Educational and training programs for the university and motivated higher level K-12 students.