Current Status of PS1 Sky Survey
and Lulin 2-m Telescope
Kinoshita Daisuke, Wu Ching-Huang, Chen Tse-Chuan,
Huang Ru-Huei, Shen Pei-Hsien, Yang Hui-Hsin
Institute of Astronomy, National Central University
CPS Seminar at Kobe Univ.
2 February 2011

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Outline
Pan-STARRS
2-m Telescope
4-Color Simultaneous Imager
ScienceDesignCurrent Status

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Visible 4-color simultaneous imager
is the 1st generation instrumentfor 2-m telescope.

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Why do we need 2-m telescope?

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Pan-STARRS

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Pan-STARRS
Panoramic Survey Telescope
And Rapid Response System
cyclical sky survey
four 1.8-m telescopes (F/4)
1.4G pix camera (FOV: 7 deg2 )0.3 arcsec per pixel
6,000 deg2 per night
detector: orthogonal transfer
CCDs (on-chip guiding)limiting mag. = 24 mag (5σ )PS1 at Haleakala,PS4 at Mauna Kea

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Pan-STARRS Minor Planet Summary

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Current Status of PS1 Sky Survey
PS1 Sky Survey officially started in May 2010.
2.5 yr operation (with possible 0.5 yr extension of themission)
Discoveries of a comet, TNOs, and NEOs
comet P/2010 T2 (PANSTARRS) (IAUC 9173)
3 TNOs
PHO: 2010 ST34-Color Imager – p.8/47

Opposition Sweet Spot Survey

OC (Observing Cycle) 133 (Oct-Nov 2010)

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MOPS Derived Objects

03/Nov/2010
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NEO Discoveries

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How to search young families?
Comparison of orbital elements of two objects
semimajor axis
eccentricity
inclination
longitude of ascending nodeargument of perihelion
Amount of calculations is the order of O(N2 ).
We need a smart way...
KD-treemachine learning, heuristic approach
GPGPU
a collaboration with a group at Computer ScienceDepartment.
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How to search young families?
Kinoshita’s test program using OpenMP
written in C with OpenMPa single computer with 2 quad-core CPUsa few hours to complete the calculation (> 0.5Mobjects)
A code by NCU Computer Science group
written in C using MPI
We have actually found some pairs which are not in anypublication.
Some astrometric observations done in Nov/2010.
Color measurements using a new 2K × 4K areplanned in Jan/2011.
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Search for small ∆V objects
Search for small ∆V objects for space missions
Hayabusa 2, Marco Polo
Solar system sweet spot survey
western sky in the evening
eastern sky in the morninga, e, i → ∆V

Having more mission candidates as back-up targets isextremely useful.
List of small ∆V object from Pan-STARRS database.
Coordinated observations by Taiwan-Japan
collaboration.

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Lulin 2-m Telescope and 4-Color Imager
New discoveries by PS1 sky surveys
Quick follow-up observations
by 2-m telescope

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Our 2-m Telescope in March 2010

in Kyoto, Japan, 08/Mar/2010
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Why visible 4-color simultaneousimager?

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Multi-color photometry
PS1 3π survey
powerful cyclical wide-field survey in g’r’i’z’ydifferent passband data acquired on different nightcolor measurements of a single object may not be
reliable enough...
asteroid rotation → change in cross-section
transient objects have variability for their nature.
2-m telescope as a color measurement machine!
discovery of an asteroid with peculiar orbit.
color information gives us a rough idea what it is.
primitive carbonanscious asteroid?
differentiated igneous asteroid?
if we have a small set of data, it’ll be easier to apply
for more observing time.
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Why simultaneous imaging?
Difficulty for color measurements at Lulin
Site characteristics
The sky at Lulin is variable.
Limited number of photometric night.
Nature of our targets
transient objects
moving objects
Problem for conventional method
The sky and/or target changes during the filter
exchange.

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One possible solution
Use of 2 or more telescope at the same time
A conversation with my former advisor Olivier Hainaut
at Paranal in 2001
“Here, we do not change filters, but we change
telescopes.”
We were using FORS1 on VLT UT1 and FORS2 on
VLT UT2.
Problem: expensive!

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Our solution
Dichroic beam splitting and simultaneous imaging bymultiple cameras
3 dichroic mirrors
4 bandpass filters
4 CCD imagers
Advantages of simlutaneous imaging
Higher observing efficiency
Relatively poor condition nights can also be used.
assuming that thin cloud has neutral transmittanceEasier calibration

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Advantages of Simultaneous Imaging
Required total time for conventional method
Tc = (texp + tro ) × Nband

Required total time for simultaneous imager
Ts =texp
Ethroughput+ tro

Assuming texp = 60 sec, tro = 8 sec, Nband = 4, andEthroughput = 0.8
Observing efficiency improves by a factor of ∼ 3.3.

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Conceptual Design of the Instrument
signal from telescopeobservers
i’ filter
DM2

imagesDM1
r’r’ filter

i’z’

y

SI1100_2
computer

SI1100_1
z’ filter
DM3
SI1100_3
y filter
NCUcam-1

CCD controller(UCAM controller)

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Optical Design of the Instrument

designed by Photocoding
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Design of the Instrument

designed by Photocoding
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Design of the Instrument

designed by Photocoding

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Spot Diagrams

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Dichroic Mirrors
100
Dichroic Mirror 19080

Transmittance [%]706050403020100300

400

500

600

700

800

900

1000

1100

Wavelength [nm]4-Color Imager – p.28/47

Filters Design (PS1 compatible)
100
PS1 r
PS1 i
PS1 z
PS1 y

90
80

Transmittance

7060
50
4030
20
100550

600

650

700

750

800

850

900

950

1000

1050

1100

Wavelength [nm](Asahi Spectra)
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Two Important Aspects for Development
quick delivery of the instrument for early science
on-time delivery → early scientific outputs right after
the telescope installation
important for future funding requests
in-house development to accumulate experiences
improving the ability
more possibility in the future
instrument with unique features → uniquescientific outputs
preparation for larger projects in the future

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Our Strategy for the Development
balance between quick delivery and in-housedevelopment
3 CCD cameras for r’, i’, and z’-bands
purchase of commercially available products
good enough specifications for scientificobservations
use of deep depletion CCDs of E2V
1 more CCD camera for y-band
in-house developmentuse of fully depleted CCD of Hamamatsu Photonics

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3 Cameras for r’, i’, and z’-band
E2V 44-82-1-D23 CCD chips
4K × 2K, 15 µm pixel
deep depletion CCD (thickness ∼ 40 µm)
16-bit digitization-100 deg C operation temperature
readout speed: 100, 400, and 800 MHz
Quantum efficiency:> 20% at λ = 350 nm> 35% at λ = 400 nm> 65% at λ = 500 nm> 80% at λ = 650 nm> 45% at λ = 900 nm
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First-Light Image of SI1100
M27 (Dumbbell Nebula)

Lulin 1-m Telescope + SI1100 series camera
20/Jul/2010, g’ (10 min), r’ (10 min), i’ (10 min)
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Detectors for NCUcam-1
Sensitivity at λ ∼ 1 µm is important!
mineral features of asteroids
brown dwarfs
photometric redshift
Use of fully depleted CCDs
thickness of depletion layer ∼ 100-300 µm
cf. thickness of thinned back-illuminated CCDs ∼10-20 µm
advantages
significant improvement of longer wavelength
sensitivity
negligible fringe pattern
lower cost
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Fully Depleted CCDs
Development at LBNL
2K × 4K chips
test observations at KPNO
Development by NAOJ + Hamamatsu Photonics
2k × 4K chips
Commercialization by E2V
to be available soon (?)

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Fully Depleted CCDs: QE

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Detector readout: Charge transfer
t0

t1

t2

t3

t4t5

t0

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Readout Electronics
NAOJ Messia5 + M-Front2
We turned down to have a collaboration with NAOJ...
Development of original readout electronics
with Univ. of Tokyo
Leach Controller
collaboration with Univ. of Nagoya
Lick Observatory / AET
UCAM controller

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Lick/AET UCAM Controller
timing board, clock board, DSP board, video board
flexible configurations
low noise
support from Beijing

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Schematic Diagram of NCUcam-1
computerfused silica window
dewar
cold plate 2
CCDconvertor

UCAM

vacuum pumpflat cablepre-amplifiercontroller
connector
cold headcold pathmolecular sieves
cold plate 1
cryocooler

UCAM controller
power supply

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NCUcam-1

Nov/2010
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NCUcam-1

Nov/2010
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NCUcam-1
NCUcam-1
Hamamatsu fully depleted
CCD (science grade chip)
Lick / AET UCAM CCDcontroller
cryocooler: Polycold PT-30
vacuum pump: turbo pumpdewar, temperature sensor,
temperature control systemdeveloped at NCU

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Lab. First-Light of NCUcam-1

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Readout Noise of NCUcam-1
Readout noise ∼ 5 electronscooling temperature: -100 deg C
sampling speed: 125 kHz
Good enough for us.

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Current Status
SI1100 series cameras: 3 cameras readycharacterization being done (Chen et al., Huang etal.)
NCUcam-1: OK, waiting for the delivery of our chip
(Mar/2011) (Wu et al.)test observation using 1-m tel. in May-Jul/2011
Filters: to be delivered in Feb/2011
Optics: to be delivered in Apr/2011
Control software: being developed (Shen et al.)Integration: Jun/2011
Test observation in autumn 2011 (?)
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SummaryLab. space is now ready, and lots of work is being donethere.
First-light of SI1100 cameras were achieved with 1-mtel.
We have successfully drived Hamamatsu chip in thelab.
Laboratory first-light of NCUcam-1
First-light of NCUcam-1 with 1-m tel. is planned inspring 2011.
Integration of the whole instrument in summer 2011.

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