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Sodium all-sky imager for the South Pole station

Sodium all-sky imager for the South Pole station. Biff Williams, NWRA/CoRA, Boulder, Colorado In collaboration with: Scott Palo and the meteor radar group at CU, Boulder Diego Janches, NWRA/CoRA, Boulder John Plane, University of Leeds, U.K Funded by OPP under NSF grant ANT-0538672.

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Sodium all-sky imager for the South Pole station

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  1. Sodium all-sky imager for the South Pole station Biff Williams, NWRA/CoRA, Boulder, Colorado In collaboration with: Scott Palo and the meteor radar group at CU, Boulder Diego Janches, NWRA/CoRA, Boulder John Plane, University of Leeds, U.K Funded by OPP under NSF grant ANT-0538672 NWRA/CoRA South Pole Workshop 2007

  2. Science Goals • Main Goal: Sodium abundance at South Pole • Look for azimuthal variation in Na abundance • Previous lidar measurements showed the winter sodium abundance to be twice as large as models. • Wind convergence or meteor influx at the pole might supply additional sodium • Use Na nightglow and model to calculate Na abundance • Measure meteor influx and wind convergence with CU meteor radar • Secondary Goal: Atmospheric dynamics • Images of gravity wave intrinsic parameters and breaking • Tertiary Goal: We could provide auroral 557nm images, if necessary. NWRA/CoRA South Pole Workshop 2007

  3. Imager: Keo Sentry 3i • Popular for nightglow and auroral studies • Telecentric all-sky system with six 3” filters • Size: 34” long, 12” wide. Weight: 28 pounds • Low power draw: ~1kW mostly from water chiller and computer NWRA/CoRA South Pole Workshop 2007

  4. CCD Camera • Finger Lakes Proline 1001E • Kodak KAF 1001E CCD chip • 1024x1024 pixels, 25x25mm • ~70%QE at 589nm, blue enhanced • lower dark noise than SITe chips • Cooling: 240K to reduce dark noise • double Peltier cooler (-50C) • Water chiller at ~5C • Bin pixels 2x2 on chip to reduce read noise and data rate • New, cost-effective design, but reliability of cooler and vacuum seal needs to be tested. NWRA/CoRA South Pole Workshop 2007

  5. Filter Wheel • 6 position filter wheel, 3 slots open • Filter wheel temperature controlled at slightly above ambient • Na (D1 + D2) filter: 589nm, 2nm FWHM, T=81% • Na background: 572nm, 2nm FWHM, T=82% • Green line: 557nm, 2nm FWHM • Old 2in filter, so 1200 FOV • Occasional 15 sec exposures for OI nightglow or aurora • Any other wavelengths of interest to other groups? NWRA/CoRA South Pole Workshop 2007

  6. Software and Data Rate • Linux operating system • Command line C program to move filter wheel (RS232) and run camera (USB) • Images are 512 x 512 x 16 bit = 0.5 MB • Image cadence: every 1-2 min when dark • About 0.7 GB/day (worst case) saved to external hard drive • Swap external drive each summer • Small status text file to download daily • Download thumbnail images if possible NWRA/CoRA South Pole Workshop 2007

  7. Calibration for sodium abundance • Operate the imager near the sodium lidars at ALOMAR, Norway (69N) and Colorado (40N) • Determine empirical relation between imager counts and Na density • Correction for South Pole: • different temperatures (measured by FPI) • atomic O concentrations (modeled) • atmospheric transmission • Hotpay2 rocket campaign in Norway • Na photometers on rocket give height profile of Na nightglow • Ground based Na spectrometer • Scheduled for October, possibly delayed. NWRA/CoRA South Pole Workshop 2007

  8. Site Considerations • Dark skies (1-2 min exposures) • 6-12 inch hole in the roof (size depends on roof thickness) • Clear view to within 200of horizon • Imager is automated, so maintenance access in the winter would be helpful, but not required. NWRA/CoRA South Pole Workshop 2007

  9. Current Status and Plans • System and software being tested at CoRA. • Next week: Ship to ALOMAR (69N) in Norway for testing and calibration with the Na lidar over the winter. • March 2008: Ship back to Colorado for further testing with the CSU Na lidar over the summer. • Aug 2008: Ship to South Pole. • Jan 2009: Travel to South Pole to install. • Run at South Pole for 3 or more years. NWRA/CoRA South Pole Workshop 2007

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