Sky and Telescope - February 2017 - 31

Other Projects in China's Future
◗ China's professional astronomical community is growing
rapidly, and its researchers are planning several major new
facilities both on the ground and in space.
Hard X-ray Modulation Telescope (HXMT) will be China's
first orbiting X-ray observatory. Proposed by Li Tipei and Wu
Mei of the Chinese Academy of Sciences' Institute of High
Energy Physics in 1993 and officially approved in 2011, HXMT
will: (1) scan the galactic plane to find new transient sources
and to monitor known ones, and (2) observe X-ray binaries to
study the dynamics and emission mechanisms in strong gravitational or magnetic fields. HXMT carries low-, medium-, and
high-energy X-ray telescopes that cover energies from 1 to 250
keV. The spacecraft is complete and ready for launch.
Large Optical-infrared Telescope (LOT), with an aperture of
12 m, would serve as a general-purpose telescope most likely
located at a high-altitude site in Tibet's Ali Prefecture. The
government has given this project preliminary approval, and
construction could begin as soon as 2019. In that case LOT

A day later they targeted a pulsar near zenith, J1921+2153,
and it took just 1 minute to achieve a signal-to-noise ratio of
more than 5,000!
For now, observers using FAST will have to settle for such
short integration times, because two signiﬁcant actuator
problems have prevented any real-time tracking. First, the
optical ﬁbers that interconnect the actuators are behaving
unpredictably, raising the possibility that errant commands
received while adjusting the dish's surface might actually lead
to damage. Second, the actuators themselves are wearing out
much faster than expected, and they will likely all be replaced.
Until these problems are ﬁ xed, FAST's observations will
be restricted and no real-time tracking will be attempted.
Instead, plans call for deforming the dish so that it points
toward one spot for an entire day, allowing radio sources
to glide across the 2-arcminute-wide ﬁeld of view. Then the
declination will be adjusted slightly to sweep through a new
strip of sky.
It will take roughly seven months of this shift-and-stare
mode for the CSIRO multi-beam receiver to cover all of the
sky that FAST can observe - everything that passes within
40° of zenith. But the effort should yield as many as 1,000
new pulsar discoveries, all detected at the atomic-hydrogen
emission at 1.4 GHz (21 cm in wavelength).
Once all the equipment tune-ups and ﬁ xes are ﬁnished,
FAST should start producing amazing results. It has nearly
twice the collecting area of Arecibo's dish - which, although
305 m (1,000 feet) across, has an effective aperture of only
225 m for astronomical observations. FAST's areal advantage,
combined with its paraboloidal focus, should permit the new

would briefly rank (until the era of 30-m facilities begins) as the
world's largest optical telescope.
Thirty Meter Telescope (TMT), an ambitious, international joint project involving six countries and institutions, will
become the most advanced and powerful optical telescope
on Earth. The National Astronomical Observatories of China
(NAOC) is funding 10% of the project, including "in-kind" contributions. For example, NAOC has participated in designing
TMT's primary (M1) and tertiary (M3) mirrors, laser guide-star
facility, and first-generation scientific instruments.
110-m Qitai Radio Telescope will have a fully steerable
receiver located near Qitai in the Xinjiang Uyghur Autonomous Region (200 km northeast of Urumqi). Developed by the
Chinese Academy of Sciences' Xinjiang Astronomical Observatory, this dish will have a deformable surface and cover the
frequency range from 150 MHz to 115 GHz. Construction has
not yet begun; however, once finished, it will be the largest fully
steerable radio telescope in the world.

telescope to probe the radio universe three times deeper,
complete surveys 10 times faster, and cover four times more
sky than Arecibo can.
(It must be noted that, although Arecibo now ranks second
in aperture, it can conduct radar observations of solar-system
targets - a capability that FAST will never have.)
Chinese astronomers expect to use FAST to discover thousands of new pulsars within our galaxy and to search for
the ﬁrst extragalactic pulsars beyond the Magellanic Clouds.
They'll also map the interstellar medium's abundances of
hydrogen and carbon monoxide (CO) at high resolution, hunt
for previously unseen clouds of neutral hydrogen, and detect
hydrogen's 21-cm emission from hundreds of thousands of
galaxies up to 6 billion light-years away.
Also on FAST's "to do" list is searching for radio emissions
from exoplanets and whatever alien civilizations might be
broadcasting from them. It will participate in international
very-long-baseline interferometry (VLBI) experiments and
might someday assist in tracking ambitious deep-space explorations by future Chinese spacecraft.
Here in China people refer to FAST as Tianyan, meaning
"heaven's eye." It is still too early to estimate how this giant
new facility will inﬂuence radio astronomy. But as scientists
gradually become more familiar with FAST's capabilities,
important new discoveries will undoubtedly follow.
RENJIANG XIE is a science writer focusing on developments in

Chinese astronomy. He's president of Dalian Boötes Astronomical Society and runs China's largest astronomy website.
Reach him at facebook.com/renjiangxie.
s k y a n d t e l e s c o p e .c o m

* FEBRUARY 2017

http://www.facebook.com/renjiangxie http://www.skyandtelescope.com

Sky and Telescope - February 2017

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