Instruments
High-level overviews of the LSST Camera (LSSTCam), the Commissioning Camera (ComCam), and the LSST Atmospheric Transmission Imager and Slitless Spectrograph (LATISS) are provided on this page.
Technical details and diagrams can be found in the Camera Tech Notes.
LSST Camera (LSSTCam)
The LSST Camera is the world's largest digital camera. It has 3.2 Gigapixels over a 9.6 square degree field of view and six optical filters.
LSSTCam is the only instrument used for the LSST, and its processed data products will be available for scientists to analyze.
See also the camera webpage for a public audience.
Focal plane
The LSST Camera focal plane is composed of 189 individual science charge-coupled devices (CCDs), arranged into 21 "rafts," along with 8 wavefront and 8 guider CCDs located in 4 additional corner rafts. Each pixel is 0.2 arcseconds on the sky, and so each CCD of approximately 4,000 by 4,000 pixels covers 13.3 by 13.3 arcminutes (0.22 by 0.22 degrees). Every CCD has 16 amplifiers, each reading 1 million pixels, enabling the full focal plane of of 3.2 Gigapixels to be read out in 2 seconds.
The CCDs were supplied by two vendors, ITL and e2v. All nine detectors in a given raft are from the same vendor. Differences between sensors are accounted for during the Instrument Signature Removal (ISR) stage of image processing by the LSST Science Pipelines.
Key numbers
Except for the gap sizes, these numbers come from Table 6 of SITCOMTN-148.
- Inter-raft gap size (x, y) [mm]: 0.50, 0.50
- Inter-sensor gap size, (x, y) [mm]: 0.28, 0.25 (e2v); 0.27, 0.27 (ITL)
- Serial charge transfer inefficiency [%]: 7.3 e-6 (e2v); 1.5 e-4 (ITL)
- Parallel charge transfer inefficiency [%]: 1.1 e-5 (e2v); 1.2 e-6 (ITL)
- Dark current [e-/pix/s]: 0.023 (e2v); 0.021 (ITL)
- Photon Transfer Curve (PTC) turnoff [e-]: 103000 (e2v); 129000 (ITL)
- Read noise [e-]: 5.40 (e2v); 6.21 (ITL)
- Gain [e-/ADU]: 1.51 (e2v); 1.68 (ITL)
References
- LSST camera electro-optical test results, LSST Camera group (2025; SITCOMTN-148)
- LSST camera verification testing and characterization, Roodman et al. (2024; SPIE)
- Integrating the LSST camera, Lange et al. (2024; SPIE)
- LSST camera focal plane optimization, Utsumi et al. (2024; SPIE)
Components
The LSST Camera is about 1.65 meters across and 3 meters long, and contains lenses, filters, shutter, sensors, cryostats and electronics.
The shutter's two sides slide back and forth to expose and then cover the focal plane. The nominal shutter open/close time is 1 second.
The filter changer mechanism - which holds 5 of the 6 LSST filters at a time - moves a filter in and out of the light path. The nominal filter change time is 2 minutes.
Filters
The LSST's six filters are u, g, r, i, z, and y. At any given time, five will be loaded into the camera's filter carousel, with a sixth filter swapped in every couple of weeks (depending on moon illumination, survey strategy, etc.).
For each filter, the effective wavelength - defined as the mean wavelength by the system response in energy units - and the full width at have maximum (FWHM) - defined as the wavelength interval between the points where the system throughput drops to 50% of its peak value - are shown in the following table.
Band | eff_wavelen (nm) | fwhm (nm) |
|---|---|---|
u | 372.4 | 46.3 |
g | 480.7 | 148.5 |
r | 622.1 | 139.9 |
i | 755.9 | 128.6 |
z | 868.0 | 104.0 |
y | 975.3 | 86.2 |
Commissioning Camera (ComCam)
ComCam was mounted on the Simonyi Survey Telescope for seven weeks in late 2024. It is a smaller, fully functional version of LSSTCam, with only the central raft of 9 CCDs (all ITL sensors). ComCam was designed to enable end-to-end testing of the observatory’s systems, including data acquisition, image processing, and observatory operations.
ComCam data products are included in the data releases for the Early Science Program.
References
- Rubin commissioning camera: integration, functional testing, and lab performance, Stalder et al. (2020; SPIE)
- Rubin Observatory Commissioning Camera: summit integration, Stalder et al. (2022; SPIE)
- An interim report on the ComCam on-sky campaign, Rubin Observatory (2025; SITCOMTN-149)
LSST Atmospheric Transmission Imager and Slitless Spectrograph (LATISS)
LATISS is installed on the Auxiliary Telescope, a 1.2-meter telescope dedicated to atmospheric characterization at the Rubin Observatory site. It is designed to measure atmospheric transmission and calibrate LSST observations by taking spectra of standard stars.
LATISS data is used by Rubin staff in the processing and calibration of the LSST data products released for scientific analysis.
References
- LATISS Instrument Handbook, Mondrik et al. (2019; TSTN-006)
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