The Integration and Verification Testing of the Large Synoptic Survey Telescope (LSST) Camera is described. The LSST Camera will be the largest astronomical camera ever constructed, featuring a 3.2 giga-pixel focal plane mosaic of 189 CCDs with in-vacuum controllers and readout, dedicated guider and wavefront CCDs, a three element corrector with a 1.6-meter diameter initial optic, six optical filters covering wavelengths from 320 to 1000 nm with a novel filter exchange mechanism, and camera-control and data acquisition capable of digitizing each image in two seconds. In this paper, we describe the integration processes under way to assemble the Camera and the associated verification testing program. The Camera assembly proceeds along two parallel paths: one for the focal plane and cryostat and the other for the Camera structure itself. A range of verification tests will be performed interspersed with assembly to verify design requirements with a test-as-you-build methodology. Ultimately, the cryostat will be installed into the Camera structure as the two assembly paths merge, and a suite of final Camera system tests performed. The LSST Camera is scheduled for completion and delivery to the LSST observatory in 2020.
The Large Synoptic Survey Telescope, under construction in Chile, is an 8.4 m optical survey telescope with a dedicated 3.2 Giga-pixel camera. The design and construction of the camera is spearheaded at SLAC National Accelerator Laboratory and here we present a general overview of the camera integration and test activities. An overview of the methodologies used for the planning and management of this subsystem will be given, along with a high-level summary of the status of the major pieces of I&T hardware. Finally a brief update will be given on the current state of the LSST Camera integration and testing program.
We present an overview of the Integration and Verification Testing activities of the Large Synoptic Survey Telescope (LSST) Camera at the SLAC National Accelerator Lab (SLAC). The LSST Camera, the sole instrument for LSST and under construction now, is comprised of a 3.2 Giga-pixel imager and a three element corrector with a 3.5 degree diameter field of view. LSST Camera Integration and Test will be taking place over the next four years, with final delivery to the LSST observatory anticipated in early 2020. We outline the planning for Integration and Test, describe some of the key verification hardware systems being developed, and identify some of the more complicated assembly/integration activities. Specific details of integration and verification hardware systems will be discussed, highlighting some of the technical challenges anticipated.
The Linear Coherent Light Source (LCLS), a free electron laser operating from 250eV to10keV at 120Hz, is opening windows on new science in biology, chemistry, and solid state, atomic, and plasma physics1,2. The FEL provides coherent x-rays in femtosecond pulses of unprecedented intensity. This allows the study of materials on up to 3 orders of magnitude shorter time scales than previously possible. Many experiments at the LCLS require a detector that can image scattered x-rays on a per-shot basis with high efficiency and excellent spatial resolution over a large solid angle and both good S/N (for single-photon counting) and large dynamic range (required for the new coherent x-ray diffractive imaging technique3). The Cornell-SLAC Pixel Array Detector (CSPAD) has been developed to meet these requirements. SLAC has built, characterized, and installed three full camera systems at the CXI and XPP hutches at LCLS. This paper describes the camera system and its characterization and performance.
The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, telescope design feeding a camera system that
includes a set of broad-band filters and three refractive corrector lenses to produce a flat field at the focal plane with a
wide field of view. Optical design of the camera lenses and filters is integrated in with the optical design of telescope
mirrors to optimize performance. We discuss the rationale for the LSST camera optics design, describe the methodology
for fabricating, coating, mounting and testing the lenses and filters, and present the results of detailed analyses
demonstrating that the camera optics will meet their performance goals.
The Large Synoptic Survey Telescope (LSST) is a large aperture, wide-field facility designed to provide deep images of
half the sky every few nights. There is only a single instrument on the telescope, a 9.6 square degree visible-band
camera, which is mounted close to the secondary mirror, and points down toward the tertiary. The requirements of the
LSST camera present substantial technical design challenges. To cover the entire 0.35 to 1 μm visible band, the camera
incorporates an array of 189 over-depleted bulk silicon CCDs with 10 μm pixels. The CCDs are assembled into 3 x 3
"rafts", which are then mounted to a silicon carbide grid to achieve a total focal plane flatness of 15 μm p-v. The CCDs
have 16 amplifiers per chip, enabling the entire 3.2 Gigapixel image to be read out in 2 seconds. Unlike previous
astronomical cameras, a vast majority of the focal plane electronics are housed in the cryostat, which uses a mixed
refrigerant Joule-Thompson system to maintain a -100ºC sensor temperature. The shutter mechanism uses a 3 blade
stack design and a hall-effect sensor to achieve high resolution and uniformity. There are 5 filters stored in a carousel
around the cryostat and the auto changer requires a dual guide system to control its position due to severe space
constraints. This paper presents an overview of the current state of the camera design and development plan.
The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, modified Paul-Baker design,
with an 8.4-meter primary mirror, a 3.4-m secondary, and a 5.0-m tertiary feeding a refractive camera design with 3
lenses (0.69-1.55m) and a set of broadband filters/corrector lenses. Performance is excellent over a 9.6 square
degree field and ultraviolet to near infrared wavelengths.
We describe the image quality error budget analysis methodology which includes effects from optical and
optomechanical considerations such as index inhomogeneity, fabrication and null-testing error, temperature
gradients, gravity, pressure, stress, birefringence, and vibration.
The Large Synoptic Survey Telescope is a complex hardware - software system of systems, making up a highly
automated observatory in the form of an 8.4m wide-field telescope, a 3.2 billion pixel camera, and a peta-scale data
processing and archiving system. As a project, the LSST is using model based systems engineering (MBSE)
methodology for developing the overall system architecture coded with the Systems Modeling Language (SysML).
With SysML we use a recursive process to establish three-fold relationships between requirements, logical & physical
structural component definitions, and overall behavior (activities and sequences) at successively deeper levels of
abstraction and detail. Using this process we have analyzed and refined the LSST system design, ensuring the
consistency and completeness of the full set of requirements and their match to associated system structure and
behavior. As the recursion process proceeds to deeper levels we derive more detailed requirements and specifications,
and ensure their traceability. We also expose, define, and specify critical system interfaces, physical and information
flows, and clarify the logic and control flows governing system behavior. The resulting integrated model database is
used to generate documentation and specifications and will evolve to support activities from construction through final
integration, test, and commissioning, serving as a living representation of the LSST as designed and built. We discuss
the methodology and present several examples of its application to specific systems engineering challenges in the LSST
The LSST camera is a tightly packaged, hermetically-sealed system that is cantilevered into the main beam of the LSST
telescope. It is comprised of three refractive lenses, on-board storage for five large filters, a high-precision shutter, and a
cryostat that houses the 3.2 giga-pixel CCD focal plane along with its support electronics. The physically large optics
and focal plane demand large structural elements to support them, but the overall size of the camera and its components
must be minimized to reduce impact on the image stability. Also, focal plane and optics motions must be minimized to
reduce systematic errors in image reconstruction. Design and analysis for the camera body and cryostat will be detailed.
The LSST camera is a wide-field optical (0.35-1μm) imager designed to provide a 3.5 degree FOV with 0.2
arcsecond/pixel sampling. The detector format will be a circular mosaic providing approximately 3.2 Gigapixels per
image. The camera includes a filter mechanism and shuttering capability. It is positioned in the middle of the telescope
where cross-sectional area is constrained by optical vignetting and where heat dissipation must be controlled to limit
thermal gradients in the optical beam. The fast f/1.2 beam will require tight tolerances on the focal plane mechanical
assembly. The focal plane array operates at a temperature of approximately -100°C to achieve desired detector performance. The
focal plane array is contained within a cryostat which incorporates detector front-end electronics and thermal control.
The cryostat lens serves as an entrance window and vacuum seal for the cryostat. Similarly, the camera body lens serves
as an entrance window and gas seal for the camera housing, which is filled with a suitable gas to provide the operating
environment for the shutter and filter change mechanisms. The filter carousel accommodates 5 filters, each 75 cm in diameter, for rapid exchange without external intervention.
The LSST camera is a wide-field optical (0.35-1um) imager designed to provide a 3.5 degree FOV with better than 0.2 arcsecond sampling. The detector format will be a circular mosaic providing approximately 3.2 Gigapixels per image. The camera includes a filter mechanism and, shuttering capability. It is positioned in the middle of the telescope where cross-sectional area is constrained by optical vignetting and heat dissipation must be controlled to limit thermal gradients in the optical beam. The fast, f/1.2 beam will require tight tolerances on the focal plane mechanical assembly.
The focal plane array operates at a temperature of approximately -100°C to achieve desired detector performance. The focal plane array is contained within an evacuated cryostat, which incorporates detector front-end electronics and thermal control. The cryostat lens serves as an entrance window and vacuum seal for the cryostat. Similarly, the camera body lens serves as an entrance window and gas seal for the camera housing, which is filled with a suitable gas to provide the operating environment for the shutter and filter change mechanisms. The filter carousel can accommodate 5 filters, each 75 cm in diameter, for rapid exchange without external intervention.