Focal Plane Requirements

• High QE to 1000nm
• Thick silicon (> 100 µm)
• PSF << 0.7 arcseconds
  • High internal field in the sensor
  • High resistivity silicon substrate (> 5 kohm/cm)
  • High applied voltages (40 - 50 Volts)
  • Small pixel size (0.2 arcseconds = 10 µm)
• Fast f/1.2 focal ratio
  • Sensor flatness < 5µm p-v
  • Package with piston, tip, tilt adj. to ~1µm
• Wide Field of View
  • ~ 3200 square cm focal plane
  • > 189-sensor mosaic (~16 square cm each)
  • Industrialized production processes
• High throughput
  • > 90% fill factor. 4-side buttable package, sub-mm gaps
• Fast readout (2 sec)
  • Segmented sensors (3024 total output ports )
  • 150 connections per sensor
• Low read noise
  • < 10 electrons

Focal Plane Design

• FPA is 189 4K x 4K CCDs, each with 16 outputs
  • 3024 video channels/FPA total
• Sensors organized into identical rafts of 3 x 3 sensors
• Clocking of Science CCDs is synchronous and global throughout the FPA
  • 500 kpix/sec * 16 outputs/CCD * 189 CCDs = 3.2 Gpix/2sec
• A raft is an autonomous object and can function as a complete camera
  • 144 channels/raft
  • readout electronics fit in "shadow" of sensors
• Raft functions as a dumb slave to OCS
• 16-bit dynamic range is handled by a single-gain readout

Camera Data Rates

• Over 3 GBytes/sec peak raw data from camera
• 1 pixel = 2 Bytes (raw)
• 3.2 billion pixels read out in 2 sec (15 sec integration)
• Dynamic Range: 18 bits / pixel
• > 0.6 GB/sec average in pipeline
• ∼15 TBytes/night
• 2 TFlops/s average, 9 TFlops/s peak

FPA Flatness Allocations Established

[1]

Sensor to Raft/Tower Configuration

[2]

Schematic of Camera Control System

[3]

Comparison of Wide Field Camera Controllers

[4]

Changer/Carousel Design

• Carousel holds five filters:g-r-i-z-y
• Rail-type changer engages carousel for automatic changing; 
• Maximum filter change time of two minutes;
• Can change filters up to four times per night; 
• Manual load-lock changer for inserting a 6th filter (u-filter);
• Operational lifetime of 2 x 104 cycles

LSST Ideal Filter Curves and Specifications

[5]

Camera Thermal Zones

[6]