Key Numbers

LSST System & Survey Key Numbers

This page lists Key Numbers that describe the LSST system and survey and is a subset of numbers available on the LSST Knowledge Base Confluence page [1]. More detailed information is available in the LSST Overview Paper [2] and Science Requirements Document [3]. (Page last updated 11/08/2018)

Optical System:
Etendue ( AΩ ) = 319 meter²degrees²
Field of View = 3.5 degrees (9.6 square degrees)
Primary mirror diameter = 8.4 m
Effective clear aperture = 6.68 m (on-axis)
Mean effective aperture = 6.423 m (area weighted over FOV)
Final f-ratio = f/1.234
Plate scale = 50.9 microns/arcsec

Imaging System:
Pixel count = 3.2 Gpixels
Readout time = 2 sec
Dynamic range = 18 bits
Pixel pitch = 10 micron (0.2 arcsec)

Spectral Response:
Full bandpass range = 320-1050 nm
Total number of filters = 6
Number of active filters = 5
System 50% response points (nm)
u 324 395
g 405 552
r 552 691
i 691 818
z 818 921
y 922 997

Survey Area:
Fiducial main survey area = 18,000 deg2
Total covered area (est.) = 25,000 deg^2
(main survey + special programs)
Fiducial number of visits per pointing in the main survey = 825

Network bandwidths:
Summit (Pachón) to Base (La Serena) = 600 Gbps
Base (La Serena) to Archive (NCSA) = 2 x 100 Gbps

Observation Properties:
The standard visit = 2 x 15 sec. exposures
Exposure sequence = 1 s open shutter + 14 s dwell + 1 s close shutter = 16 s
Visit sequence = 16 s exp + 2 s readout + 16 sec exp = 34 s
(second readout concurrent with slew)
Median slew time between visits = 4.8 s
Mean slew time between visits = 6.8 s
Visits per night = "about a 1000"
Calibration exposures = 450/day
Data collected per 24 hr period = "about 20 TB"

Data Releases:
Number of Data Releases = 11
Date of DR1 release = Date of Operations Start+ 12 months
Estimated counts for DR1 release
Objects = 18 billion
Sources = 350 billion (single epoch)
Forced Sources = 0.75 trillion

Estimated counts for DR11
Objects = 37 billion
Sources = 7 trillion (single epoch)
Forced Sources = 30 trillion
Visits observed = 2.75 million
Images collected = 5.5 million 3.2 Gigapixel images

Alert Production:
Real-time alert latency = 60 seconds
Estimated number of alerts per night= up to about 10 million

Data and compute sizes:
Final volume of raw image data = 60 PB
Final image collection (DR11) = 0.5 Exabytes
Final catalog size (DR11) = 15 PB
Final disk storage = 0.4 Exabytes
Peak number of nodes = 1750 nodes
Peak compute power in LSST data centers = about 2 PFLOPS