A Broadband Digital Spectrometer for the Deep Space Network

The Deep Space Network (DSN) enables NASA to communicate with its spacecraft in deep space.By virtue of its large antennas, the DSN can also be used as a powerful instrument for radio astronomy.Specically, Deep Space Station (DSS) 43, the 70 m antenna at the Canberra Deep Space Communi-cations Complex (CDSCC) has a K-band radio astronomy system covering a 10 GHz bandwidth at17 GHz to 27 GHz. This spectral range covers a number of atomic and molecular lines, produced ina rich variety of interstellar gas conditions. Lines include hydrogen radio recombination lines (RRLs),cyclopropenylidene (C3H2), water masers (H2O), and ammonia (NH3). A new high-resolution spec-trometer was deployed at CDSCC in November 2019 and connected to the K-band downconverter.The spectrometer has a total bandwidth of 16 GHz. Such a large total bandwidth enables, for ex-ample, the simultaneous observations of a large number of RRLs, which can be combined together tosignicantly improve the sensitivity of these observations. The system has two rmware modes: 1)A 65k-pt FFT to provide 32768 spectral channels at 30.5 kHz and 2) A 16k-pt polyphase lterbank(PFB) to provide 8192 spectral channels with 122 kHz resolution. The observation process is designedto maximize autonomy, from the Principle Investigator's inputs to the output data in FITS le format.We present preliminary mapping observations of hydrogen RRLs in Orion KL mapping taken usingthe new spectrometer.