Sky & Telescope - June 2024 - 36

Next-Generation Telescope
After considering locations in Mexico, the Canary Islands,
and Chile, astronomers selected Cerro Pachón in 2006 as
the best location for Rubin. This was partly because of the
existing infrastructure - the mountaintop (not too far from
Cerro Tololo) is already home to the 8.1-meter Gemini South
telescope and the 4.1-meter Southern Astrophysical Research
Telescope (SOAR).
The project received the official green light in August 2014,
and the ceremonial " unveiling of the first stone " was done on
April 14, 2015, by Chilean president Michelle Bachelet. The
lion's share of the $670 million construction cost has been
ponied up by the National Science Foundation (NSF) and the
Department of Energy (DOE), with smaller contributions
from private donors like Microsoft's Bill Gates and Charles
Simonyi, after whom the telescope is officially named. NSF's
NOIRLab will operate and manage the facility.
Back in 2014, planners hoped the observatory would be
ready in 2022. " The COVID pandemic has been the major
source of construction delays, " says Krabbendam, " but right
now, everything is coming together quite nicely. "
The telescope's three-mirror design is like no other. Its
8.4-meter primary mirror (M1) is among the largest monolithic
telescope mirrors ever built, and it's actually two
mirrors in one: The central part, 5 meters in diameter, has
a much stronger curvature and acts as the instrument's
tertiary mirror (M3). Grinding and polishing both mirrors
from one huge slab of glass ensured a very stiff optical
system. Although it's impressively large, the telescope is also
extremely compact: The 3.4-meter convex secondary (M2)
sits less than 6.5 meters above M1, resulting in a very wide
field of view 3.5 degrees across - as wide as seven full Moons.
Each image obtained by Rubin will cover almost 10 square
degrees, which is about as large as the head of the constellation
Hydra, the Water Snake.
To capture such an enormous area of sky in full detail, the
Rubin Observatory LSST Camera, designed and built by the
DOE's SLAC National Accelerator Laboratory in California,
features a 25-inch-diameter focal plane, covered by 189 CCDs
of 16 million pixels each. As large as a car and weighing
almost 3 tons, it is the largest astronomical camera ever built,
sporting a whopping 3.2 billion 0.01-millimeter-wide pixels
in total, with a resolution of 0.2 arcsecond per pixel. According
to Beth Willman, the CEO of the LSST Discovery Alliance,
in order to display one Rubin image at full resolution
11-meter wind/light screen
THE OBSERVATORY Much more
than a dome, the observatory building
houses equipment needed to care for
the telescope, including a chamber for
recoating the mirrors.
30-meter dome
350-ton
telescope,
camera,
and mount
16-meter
telescope pier
27-meter vertical
platform lift
Camera clean room
75-ton M1/M3 telescope cell
Coating chamber
Control room
Machine shop
36 JUNE 2024 * SKY & TELESCOPE
RUBIN OBSERVATORY / J. ANDREW
Sky & Telescope - June 2024

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