LSST H2RG Guider Testing:
We have just set up a laboratory at Stanford
to do testing for the Large Synoptic Survey Telescope (LSST) guider subsystem. We will use a HyViSI H2RG and
laser spot projection system to do centroid accuracy measurements as a function of clocking frequency and
star brightness. The hybrid CMOS design is well suited for guiding since the same frame rate can be obtained
for a star independent of its location on the detector.
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Hybrid CMOS H4RG Detector:
I'm currently involved in an effort to test and characterize the Teledyne H4RG 16 MegaPixel camera as a
potential sensor for the LSST guider. The H4RG is a Hybrid Visible Silicon (HyViSi) CMOS imager, different
from the Charge Coupled Devices (CCDs) usually used in optical astronomy. CMOS imagers present a number of very appealing features for astronomy, such as
high speed photometry of stars.
To the right is a picture of M57 taken with the H4RG. It is a combination of 3 minute exposures using G (400-600 nm) and I (670-800 nm) filters.
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SIDECAR ASIC Software Development:
I have been developing software and assembly code for the
SIDECAR ASIC
produced by
Teledyne Scientific. This is the chip that will
replace
the control electronics for the Hubble
Advance Camera for Surveys (ACS)
and control the detectors on board the future
James Webb Space Telescope (JWST).
I am continually modifying the microcontroller assembly code to acheive
better noise performance and implement additional functionality such as
onboard centroiding. If you are an astronomer that is using this chip and
would like a distribution of the code, please email me.
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Atmosphere Turbulence and its Effect on Image Ellipticity
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Atmospheric turbulence isn't just a pain in the butt for pilots in small airplanes; it's
also a huge problem for astronomers. Usually described as Kolmogorov turbulence, it
causes random spatial and temporal fluctuations of density and temperature in the air between
us and the stars. These fluctuations cause stars to twinkle, or scintillate, and take on a shape
different from the Airy Disc we'd expect from a point like object. Instead, the star can be distorted
from their round shape and take on a non-zero ellipticity.
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Cosmic Ray Simulation in LSST Detectors:
We're trying to model cosmic ray events in the LSST detectors with the
GEANT4 software package. The purprose is to identify and
characterize the events in each frame while also trying to understand
their origin. And more importantly, try to figure out how to separate
cosmic rays from fast transient celestial events such as stellar
flares.
Eventually, the simulations will be compared to data from existing
large aperture telescopes.
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