  The Greenland Telescope project has recently participated in an experiment to
image the supermassive black hole shadow at the center of M87 using Very Long
Baseline Interferometry technique in April of 2018. The antenna consists of the
12-m ALMA North American prototype antenna that was modified to support two
auxiliary side containers and to withstand an extremely cold environment. The
telescope is currently at Thule Air Base in Greenland with the long-term goal
to move the telescope over the Greenland ice sheet to Summit Station. The GLT
currently has a single cryostat which houses three dual polarization receivers
that cover 84-96 GHz, 213-243 GHz and 271-377 GHz bands. A hydrogen maser
frequency source in conjunction with high frequency synthesizers are used to
generate the local oscillator references for the receivers. The intermediate
frequency outputs of each receiver cover 4-8 GHz and are heterodyned to
baseband for digitization within a set of ROACH-2 units then formatted for
recording onto Mark-6 data recorders. A separate set of ROACH-2 units operating
in parallel provides the function of auto-correlation for real-time spectral
analysis. Due to the stringent instrumental stability requirements for
interferometry a diagnostic test system was incorporated into the design. Tying
all of the above equipment together is the fiber optic system designed to
operate in a low temperature environment and scalable to accommodate a larger
distance between the control module and telescope for Summit Station. A report
on the progress of the above electronics instrumentation system will be
provided.
