Brian Schmidt, Paul Francis, Mike Bessell, Stefan Keller
The SkyMapper Telescope
• A 1.3m telescope with
an 8-sq degree FOV
• Located at Siding
Spring Observatory
• First light in 2006
• Fully Automated
• Replacement of the
Great Melbourne
Telescope
Why SkyMapper?
• There is no deep digital map of the southern sky
and no instrument planned in the near future
that can map the entire southern sky in multiple
colours and at multiple epochs.
• Poor seeing of Australian sites a benefit – we
can use larger pixels and cover sky more
quickly.
• Science capabilities are broadly relevant to
Australian Astronomy. Matched to capabilities of
AA on the Anglo-Australian Telescope.
• Natural Replacement for the destroyed 1.3m
Great Melbourne Telescope.
Fundamental Goals of
SkyMapper
SkyMapper’s competitive advantage over other facilities
is the ability to map sky to a depth required for its
scientific goals as fast as possible, while retaining
photometric and astrometric accuracy over a wide
dynamic range of brightness and wavelength coverage.
This implies:
• Maximising the imaged field of view of the telescope
• Obtaining best possible image quality with fully sampled
pixels
• Broadband wavelength coverage from 340-1000 nm
• Minimal readout time
• Instrument which can be accurately characterised and
calibrated.
The Skymapper Telescope
.71m secondary
hyperbolic
• Being built by Electro
Optics Systems,
(Queanbeyan &
Tucson) 0.54m fused silica asphere
1.35m primary
hyperbolic
2 x 0.45m fused silica spherics
The SkyMapper Imager
268 million pixel CCD mosaic
constructed at Mount Stromlo
Observatory
•32 E2V CCD44-82 devices
•2048x4096 15
micron pixel CCDs
•Broadband coated
•40 micron Deep depletion
devices
•Leach III read out electronics,
one channel per CCD
•Read-out time 20 seconds,
readnoise 5e•6 filters slots
•Cooled using closed cycle
helium coolers
SkyMapper Science
• What is the distribution of large Solar-system objects
beyond Neptune?
• What is the history of the youngest stars in the solar
neighbourhood?
• How far does the dark matter halo of our galaxy extend
and what shape is it?
• Discovery of the metal poor stars in the halo
• Galactic Archaelogy – gravity and metallicity for
100,000,000 stars
• Accurate photometric calibration of Galaxy redshift
surveys
• Identification of z>5 quasars
• Survey of quasars by variability
• Planetary transits
• Large number of intermediate z Supernovae
• Microlensing
Virtual Observatory Optical Photometric and
Astrometric Framework
Complete sky coverage with photometry
accurate globally to 0.03 mag and
astrometry accurate, globally to 50mas.
We will do the South – and matched to
Pann-starrs in the north.
Expected Survey limits
u
g
r
i
z
21.9
21.8
21.8
20.9
20.2
540s combined
22.9
of 6 epochs
22.8
22.8
21.9
21.2
Sloan
Digital Sky
22.0
Survey
comparison
22.2
22.2
21.3
20.5
90s- 1
epoch
How Long is this going to take?
SSO Astronomical hours per year: 3285
SSO useable hours per year: 1971
Seeing
SSO obs time
(hrs/yr)
Any
<2
<1.5
<1.2
<0.9
Dark
980
656.6
490
245
98
Grey
490
328.3
245
122.5
49
Bright
490
328.3
245
122.5
49
Approximately 1000hrs per year where conditions
are better than 2” in Dark and Grey
6 colours @ 6 epochs * 4000 pointings of 120s
each yields
4800 hours of telescope time, or roughly 4.8
years. (3 epoch survey will be completed within
2.4 years)
A 5 second survey (for calibration) to be done in
Bright time as will low galactic latitude r,i,z
measurements.
Filter Choice
• Use SDSS
standard ugriz
– u to be a stellarfriendly (no flux
above 3750A)
– use vs filter (3750
-4100A) to help
with stellar work
– potentially use
Mg filter to get
gravity of K giants
How do we do?
SkyMapper filters and Tycho
bands(red)
1.00
0.80
0.60
0.40
0.20
0.00
3000
4000
5000
6000
7000
Wavelength
8000
9000
10000
SkyMapper Time
• Approx 75% of time for first 5years will go
to survey, with the survey competing for
the remaining time against other proposals
which are not covered by the survey
• Survey can observe fields preferentially as
needed by members of the community
• Data can be delivered flatfielded and with
survey software to provide calibrated data
for stars and galaxies within Hardware
limits. Specialised software is the
proposer’s responsibility
Deliverables to the Outside
User
• Data (epoch, RA, DEC, mags, galaxy
shape info,…)
to be available through a web-served
interface which provides catalogs over a
user defined area (maximum size will be
limited)
Images to be available through a webserved interface which provides images
over a used defined area (maximum size
will be limited)
How Much Data?
6 epochs x 6 colours x 4000 268,000,000 pixel
images ~150 Terabytes
3 epochs x 6 colours 5 second survey image ~75
Terabytes
+ 25 Terabytes of calibration images
1 Billion Objects observed 36 times with
Database is ~2 Terabytes (1 billion rows x 500
columns)
How Served
• Image data to be served as a tangent projected
image over a specified RA, DEC range. These
will be fully reduced and combined data and
served as FITS
• All Individual frames (reduced) will be served as
un-projected FITS files by RA DEC as full
images
• Catalog will initially be served as RA and DEC
regions only, with full relational operations on
database to be done via some allocation
process to keep within allowable resources.
Timeline
•
•
•
•
•
•
•
•
Funding Decision, Jun 2004
Optical elements ordered
Conceptual Design Review, Oct 2004
CCDs ordered, Feb 2004
Critical Design Review, July 2005
Site Works begin Dec 2005
First Light, Sep 2006
Regular Operations, 2007