Lunar Astronomy with the LUT on Chang’e-3
lander
National Astronomical Observatories, CAS/
Guangxi University
J. Wang on behalf of LUT group
Beijing
2018/12/07

Contents
 Lunar-based Ultraviolet Telescope
 Performance on the Moon
 Scientific results

The dreams to observe the Universe on the Moon
Far UV camera
with Appolo 16

 Lunar-based Ultraviolet Telescope (LUT, Cao+11)
 A small, but automatic, telescope aboard CE-3 working in NUV.
The FIRST automatic telescope landed on the extraterrestrial body in
mankind history.
 Scientific Objectives
– Monitoring variable stars
 Pulsating or binary stars, e.g., RR Lyr variables
 Variable stars in clusters
 Activities of solar-like stars
– Survey the sky
 Especially survey the low galactic latitude region;
 Violent flare stars
Lunar-based Ultraviolet Telescope I

 Milestones
– July 2004: Proposal Conception
– Feb. 2009: Project Approval
– Sep. 2009: Engineering Model
– Dec. 2011: Flight Model
– Dec. 02. 2013: Launch
– Dec. 16. 2013: First Light
– Jan. 2014 -- : Observations
– The FIRST automatic telescope on the
Moon for mankind.
LUT
First image
RA. 16:45:00
Dec 50:26:00
(Draco)
Lunar-based Ultraviolet Telescope II

Lunar Enterprise Daily,2015/01/01

A supporting system for LUT scientific obs
Exp vs S/N
Ins. setup
Finding chart & catalog
Obs sequence head
Obs sequence：
Time slot
Position of Gimbal
Rotation step
Target & comp coordinate

 Instrument Specifications
 Comp: Telescope+Pointing Reflector
Item Value
Diameter 150mm
Focal Length 562.5mm
Wavelength 245—340 nm
Field of view 1.36  1.36 Square Degrees
CCD camera E2V 47-20 UV enhanced
Working time lunar day time
Life time > one year
Weight 13.6 kg
Lunar-based Ultraviolet Telescope III

Performance on the Moon I
Sky Coverage: inside the red
circle Pointing calibration
Allow the telescope to point to any target &
trace smoothly
 Flux calibration
– ~13.5 mag in lunar day time
– ~15.5 mag with dark sky
4 images combined (dark
sky)

Data Processing
 Almost following the standard processing of
astronomical CCD photometry;
 Bias & dark corrections;
 Scattering light subtraction;
 Aperture photometry;
 Astrometry calibrations
 Flux calibrations with standard photometry stars;
 Pipelines have been developed with using the popular
astronomy software package, IRAF & Python.
Performance on the Moon V

Scattering light subtraction
 Dedicated pipelines were developed to subtract
the scattering light.
The scattering light imageCCD image
Subtracted image

Scientific results I
 Sky Survey in NUV
– Bright sources catalog (Meng+2016)
– 86 467 stars down to 16mag

Scientific results II
 Monitor of various variable stars hard to be done on ground
Identification of rapidly mass-transferring binary stars in a 6-
stars system!
AI Dra: Algol-type eclipsing binary
with P=1.1988 days.

Scientific results III
 The lowest upper limit on OH concentration in lunar
exosphere
Method Surface
concentration（cm-3)
HST spectroscopy <106(5σ)
Apollo12/14/15 CCGEs <107
Chandrayaan/CHACE <2 ×109
LUT background emission <4 ×104
Chandrayann-I M3 3μm OH absorption distrib

The End
Thanks