Ground Based Observatories (GBO) All Sky Imager Design Stewart Harris - UCB 20030818_101220_ATHA

All Sky Imager Overview Use Camera/Lens design validated in Phase A Cooled CCD camera 16-bit A/D, USB interface All Sky Lens w/ telecentric filter cell Add USB extender USB cable extends from 5m to 50m using CAT5 cable Add Environmental Enclosure Requires heating / temperature control Provides flexible mounting interface Add Sun Shield Electrical Interface Unit Test

All Sky Imager w/ USB I/F Starlight Xpress MX716

ASI Requirements REQUIREMENT SYSTEM DESIGN GB.ASI-1: FOV. The field of view of the ASI shall be greater than 170°, full angle. Compliance. Yes GB.ASI-2: Exposure Time. Shall have an exposure duration that is programmable with a maximum exposure duration of no less than 1 second. GB.ASI-3: Spectral Response. Within passband of 400 to 700nm, shall provide detectable response when stimulated with a source radiance less than 10kRayleigh, at maximum specified exposure duration. Compliance. Expect minimum sensitivity < 1kR (5:1 SNR) GB.ASI-4: Spatial Resolution. Shall provide aurora onset localization with accuracy better than 100km (dMLT< 1°) Compliance. Raw ASI image will have > 250 pixel resolution per image diameter. Thumbnails will have 0.5° binning. GB.ASI-5: Viewport. Shall have heated dome viewport GB.ASI-6: Cadence Shall have a programmable repetition interval, minimum interval of no less than 10 seconds Compliance. Have demonstrated cadence of 5s, and 3s appears to be feasible

20040225_132755_TEST_THEMIS00_VIS_1000ms ASI Data Products ASI primary image 290 pixel diameter is “binned” to 0.5° resolution (thumbnails) Primary science data: Level 1 (~ 1kbps) (incl GMAG, housekeeping) • Available via SAT comm, either Telesat (Internet real-time) or Iridium (daily) High resolution data: Level 0 (180 kbps) recorded HDD Selective downloads via Satellite Internet Periodic manual collection via disk swapping 20040225_132755_TEST_THEMIS00_VIS_1000ms

ASI Enclosure Specifications Operate in external ambient –50º to +40ºC Maintain internal temperature at 20º ± 10ºC Requires about 150 W heating Heat dome to clear it of snow/ice Hermetically sealed unit w/ nitrogen purge Dessicant used for field repair Hermetically sealed electrical connectors Polycarbonate/acrylic dome Flexible mounting

Prototype ASI Enclosure

ASI Enclosure Performance Dome: Stayed clear Some ice buildup on flange Heating: Maintain 50° T using about 35W avg. heat power Total heating power available is 240W 3/3/2004

ASI Prototype Findings “dome gunk” Courtesy M. Greffen What we learned: 5 second cadence produces a LOT of data Insulation must be tolerant to sun exposure Adopting Foil-face polyethylene air pillow wrap, multi-layer wrap Improvement to dome heating is desirable Sealing improvement needed Other minor issues: Need to reduce length of housing Improve thermal coupling of thermistor to mounting bracket Orient camera such that top of image is North Various changes in fasteners / assembly

Production Enclosure Design Design: Allison Park Group, Inc.

ASI Sun Shield Background Result ASI must survive, without degradation, non-operating exposure to daytime sun exposure CCD is Sony Interline Transfer device ICX249AL Features “microlens” on each pixel, an organic material subject to deterioration due to UV exposure All Sky Lens uses Peleng Fisheye f/3.5 A/R coating exhibited discoloration after one summer in Athabasca Result Need internal sun shield Drives housing diameter and heat required

Retracted Position is the Fail-safe Position Sun Shield Design Retracted Position is the Fail-safe Position

Sun Shield Prototype Status: Just built Needs adjustment / balancing Solenoid drive circuit needs test Provides low power cont. duty drive Needs qualification test

ASI Electrical Interface ASI has two external interface connectors: Power Data

ASI Unit Test Summary Acceptance Tests: Pre-Shipment: FOV (>170°) Exposure Time (duration at least 1 sec) Spectral Response Produce detectable response to source radiance < 10kR Goal < 1kR Passband 400 – 700nm 1 sec exposure duration Spatial Resolution (>250 pixel image diameter) Verify point source response Cadence (better than 10s) Goal < 5s Record dark and bias images (room temperature) Record response to standard source Pre-Shipment: Focus adjustment and verification Alignment verification (top of image relative to alignment datum) Heater control functional test (incl thermistor time response) Solenoid functional test (#iterations TBD) Internal mechanical inspection checklist Final Assembly / purge and backfill Final functional test and Imager Burn-in (duration TBD)