The Dark Energy Survey

Report
The Dark Energy Survey:
Dark Energy Camera – DES:
YR1 of the Dark Energy Survey
David James (CTIO)
for the Dark Energy Survey
Pan-STARRS1: Science Results
STScI, Baltimore - 24 June 2014
The Dark Energy Survey:
Ω Survey project to probe signatures of
Dark Energy using four complementary
techniques:
Ω
Ω
Ω
Ω
Cluster Counts
Weak Lensing
Large-scale Structure
Supernovae
Ω Two multiband surveys:
Ω 5000 deg2: 10σ griz(Y) to 24th (21.6th) mag
Ω 30 deg2: repeated SNe fields
Ω Build new 3 deg2 FoV camera
and data management system:
Ω Survey 2013-2018 (525 nights)
Ω Facility instrument for Blanco
Pan-STARRS1: Science Results
http://lsst.org
Blanco 4-metre Telescope at CTIO
Dark Energy Survey
David James
The DES Collaboration
Fermilab
University of Illinois at Urbana-Champaign/NCSA
Several hundred members
University of Chicago
plus students & postdocs
Lawrence Berkeley National Lab
NOAO/CTIO
Funding: DOE, NSF; UK:
DES Spain Consortium
STFC, SRIF; Spain
DES United Kingdom Consortium
Ministry of Science,
University of Michigan
Brazil: FINEP, Ministry
Ohio State University
of Science, FAPERJ;
University of Pennsylvania
Germany: Excellence
DES Brazil Consortium
Cluster; collaborating
Argonne National Laboratory
institutions
SLAC-Stanford-Santa Cruz Consortium
Universitats-Sternwarte Munchen
Texas A&M University
plus Associate members at: Brookhaven National Lab,
U. North Dakota, Paris, Taiwan
Pan-STARRS1: Science Results
Dark Energy Survey
David James
Dark Energy Camera:
A new prime focus instrument
CCD
Readout
Filters +
Shutter
Focal plane (detector, 62+ CCDs)
Hexapod
Corrector
Lenses
Pan-STARRS1: Science Results
Dark Energy Survey
David James
Brave New World: DECam
Parameter
Mosaic II
DECam
No. of CCDs
8
62 + 12(F&A, guiding)
CCD Format
2Kx4K, 15μ pixels
2Kx4K, 15μ pixels
CCD Type
Standard, BBAR
Depleted, red optimized
Full well
60K
130K
Image size
128 MB
1040 MB
RON
6-12 e- rms
15 e- rms
Read time
100s
17s
Overheads
10s
3s
Guiding
separate
Focal plane
Filters
many
grizY
ADC
yes
no
Pan-STARRS1: Science Results
Dark Energy Survey
David James
Controlling DECam: SISPI
Ω Data Flow:
Ω Image acquisition (Panview, 6 Monsoon crates)
SISPI is the DECam data
acquisition and control system:
Ω Image Builders (multiple instances)
Ω
FITS formatting
Ω
Image Health
Ω
Telemetry
Ω
Compression
Ω Submit to NCSA (DTS)
Ω Observation Control:
Ω OCS (pipeline architecture)
Ω OBSTAC
Ω Instrument Control:
Ω Internal (shutter, hexapod, filters)
Ω External (cooling, temperatures, ICC)
Ω Guider & Focus:
Ω Interfaces to TCS & Cloud Camera:
Pan-STARRS1: Science Results
Dark Energy Survey
David James
The Dark Energy Camera: Detector
2k x 2k
Focus &
Alignment
2k x 2k
Guide
2k x 2k
Focus &
Alignment
Pan-STARRS1: Science Results
2k x 2k
Guide
Dark Energy Survey
David James
(original) DES Observing Strategy:
Ω Sept-Feb observing seasons
Ω 80-100 sec exposures
Ω 2 filters per pointing (typically)
Ω gr in dark time
Ω izy in bright/grey time
Ω Photometric calibration: overlap
tilings, standard stars,
spectrophotometric calibration
system, preCAM
Ω 2 survey tilings/filter/year
Ω Interleave 10 SNe fields in griz if
non-photometric or bad seeing or
time gap (aim for ~5 day cadence)
Pan-STARRS1: Science Results
2 tilings
Dark Energy Survey
3 tilings
David James
(present) DES Observing Strategy:
Year 1:
Ω Moved footprint eastward to
reduce secZ, improve image
quality
Ω Cover 2000 sq. deg. (4 tilings per
filter) rather than full 5000 sq.
deg. (2 tilings) to improve
photometric calibration
Ω Allow g, Y observations with
seeing>1.1” (not used for Weak
Lensing).
Year 2:
Ω Complementary 3000 sq. deg.
Ω Optimize: many more half-nights
than YR1
Pan-STARRS1: Science Results
Year 1 regions
SDSS Stripe 82
SPT
By end of YR2, expect will have done
90% of the exposures needed to complete
4 tilings of the 5000 sq. deg. footprint.
Dark Energy Survey
David James
Dark Energy Survey: Year 1
Ω DES started taking YR1 data on Aug. 31st 2013
Ω In January, we switched to 1st half nights
Ω Finished YR1 in mid-February 2014
Month
# Full Nights
# 1st Half
Nights
# 2nd Half
Nights
August
1
0
0
September
24
0
0
October
14
0
0
November
18
0
0
December
27
0
0
January
4
19
0
February
0
9
0
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DES: Observing Sequences
Pan-STARRS1: Science Results
Dark Energy Survey
David James
Year 1 (vs. SVA1):
Exposure Breakdown
Time period
SVA1
YEAR1
11/01/12 − 02/15/13
08/31/13 − 02/15/14
# exposures
% accepted
# exposures
% accepted
All bands
10929*
60%
17605*
82%
g
1998
58%
4203
73%
r
2086
53%
2782
90%
i
2281
57%
2916
93%
z
2375
65%
2965
96%
Y
1608
88%
4738
70%
Pan-STARRS1: Science Results
Dark Energy Survey
David James
First DES YR1
Image
• 31st Aug. 2013 23:55
Local Chilean Time
First DES YR1 image is #229250
Ω Image DECam_00229250 was
transferred to NCSA in Urbana
where;
Ω DES “Data Management” processed
it and made a catalog of the stars and
roughly 100,000 galaxies that can be
identified in it.
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DES Operations Efficiency
Measurements
Operation
Observing Time Available
Observing Time
DES Yr. 1 Accumulated
Hrs. (%)
888.25
(100)
751.50
Engineering Observations
Bad Weather
Telescope or
Infrastructure Failure =>
can’t observe
Camera Systems Failure
=> can’t observe
Observer Error
(84.6)
NA
DES Extended SV
Hrs. (%)
321.0
(100)
226.7
(70.6)
23.2
(7.2)
90.25
(10.2)
24.5
(7.6)
18
(2.0)
45.1
(14.1)
25.75
(2.9)
1.5
(0.5)
2.75
(0.3)
0
(0.0)
Ω Only 2 problems lasted as long as 4 consecutive hours: In Oct. we lost a night from a TCS
software bug. In Nov. we lost 1½ nights due to problems w/ electronics: noise and missing
backplanes, then CCD S30 failed.
Ω The other problems are computer interfaces issues, … mostly, shutter resets
Ω Shutter was open 63% of “Observing Time” during YR1. Dome control improvements gave us
~4% better efficiency starting in late December 2013.
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DES WF
Survey
Ω Goal was to observe 4 “tiles”
of ~672 images per tile in each
of 5 filters
Ω 13435 images total
Ω Plots here show what we
obtained:
Ω Gaps in Stripe 82 (North)
Ω Gaps in Sept. to Nov. survey area
(West)
Ω Images in YR2 fields because
nothing “available” from YR1
particularly in late Jan. to Feb.
~3k images (17%) of YR2
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DES SN Survey: YR1 Observations
Ω 10 SN fields. 2 of those
are “deep fields”
Ω Our plot shows day-byday SNe cadence
Ω 2565/2699 SNe exposures
“good” (95%)
Ω After 7-days, even when
the weather is good, SNe
team gets their data on
“deadman” condition of
OBSTAC.
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DES Observing: YR2
Pan-STARRS1: Science Results
Dark Energy Survey
David James
First DES (SV) Science Paper:
2014arXiv1405.4285M
Pan-STARRS1: Science Results
Dark Energy Survey
David James
Community Use of DECam:
Ω DECam-NEOO:
Ω Lori Allen (NOAO – PI)
Ω 3-yr survey time awarded
Ω 1st 10-night block executed April
2014
Ω Early results are very
encouraging
Ω Light-echoes of SNe remnants:
Ω
Ω
Ω
Ω
Armin Rest (STSci – PI)
many nights per semester
étendue of DECam critical
latest results are now available:
Prieto et al. 2014, ApJL, 787, L8
Pan-STARRS1: Science Results
Dark Energy Survey
David James
DECam Current Status
Ω Sensor array is OK except
S30
Ω Two CCDs are no longer
functioning correctly:
Ω N30 11/07/2012
Ω S30 11/28/2013
Ω 8 CCDs ~12e- RO noise (7e- is
typical), spec is 15 e-. Problem
comes and goes since late Nov.
S7
Ω S7 (½ CCD) non-linearity unstable
at very low light levels (<1000e-).
Ω Two focus chips have 1 “weak”
amplifier.
N30
Pan-STARRS1: Science Results
Dark Energy Survey
David James
The DES Collaboration
Thank you !
Pan-STARRS1: Science Results
Dark Energy Survey
David James
The DES Collaboration
Pan-STARRS1: Science Results
Dark Energy Survey
David James
The DES Collaboration
Pan-STARRS1: Science Results
Dark Energy Survey
David James
NOAO
NCSA
sk Brian Yanny, DES Data Coordinator,
or Robert Gruendl, UIUC
24
DECam Community Workshop, Tucson, August 2011
25
DECam Community Workshop, Tucson, August 2011

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