Gemini staff contributions
On the Horizon
GHOST’s Cassegrain unit captures first light. The OCTOCAM
project receives both a new Principal Investigator and Instrument
Scientist as it nears its Preliminary Design Review. And demand is
high for the new visiting instrument IGRINS, a broad-band, high-
spectral-resolution spectrometer at Gemini South.
First Light for GHOST’s Cassegrain Unit
In January 2018, the Cassegrain unit for the Gemini High-resolution Optical SpecTrograph
(GHOST) arrived safely at Gemini South (Figure 1). It is the first of three primary assemblies
to arrive and will be mounted on the telescope’s Instrument Support Structure (ISS); the
other two are the spectrograph bench (to be located in the pier lab), and a 30-meter-long
fiber cable connecting the two. The Cassegrain unit contains the positioning arm system,
the object and sky fiber integral field units (that capture all the light), and
their corresponding atmospheric dispersion correctors.
Second of two
trucks delivering the
Cassegrain unit to Cerro
Credit: David Henderson
The Australian Astronomical Observatory designed and built the Casseg-
rain unit, with the Australian National University providing the needed
software. Members of each organization traveled from Australia to Cer-
ro Pachón in Chile to unpack, assemble, and test the unit; they also had
critical support from the Gemini South day crew, and from other Gemini
GHOST team members.
The combined teams prepared and installed the Cassegrain unit on the
telescope’s ISS to make the first checks on sky in early February (Figure 2).
The team had a successful night of testing, with the instrument perform-
ing very well. A few of the evening’s accomplishments included con-
firming that GHOSTS’ coordinate systems and field center were aligned
within our measurements, and ensuring that the probe map of the po-
sitioners was well behaved. The team also mapped the unit’s coordinate
systems to the sky, acquired targets repeatedly over the entire seven arc-