Michael Richmond's SNAP pages
Errors incurred in transferring calibration from bright stars to faint
(Oct 30, 2008)
As we go from well-calibrated stars of around mag = 11
to very faint target objects of mag = 25,
how much random statistical error builds up in our photometry?
Saturation limits for a satellite mission
(Oct 18, 2008)
How bright a star can a satellite observe without saturating
its CCD detectors?
How does "flatfield noise" scale with flatfield light level?
(Apr 17, 2008)
Just how long will we need to make our internal lamp
exposures in order to prevent the noise of the flatfields
from ruining stellar measurements?
Determining filter parameters by observing stars (Mar 14, 2008)
This is an updated version of a document from Jan 5, 2006,
which you can see below.
I have added several graphs, numerical examples, and
new explanatory text.
Rough calcultion of time to scan filter transmission curves
(Feb 27, 2008) in plain ASCII text
Summary of NICMOS calibration issues from ISRs
(Dec 12, 2007) in plain ASCII text
Notes from SNAP Calibration phone conference of Feb 8, 2007
in plain ASCII text
A tutorial for running SNAPSim (on a Linux system)
(Feb 6, 2007) I put this together for my own reference,
but perhaps other members of the calibration team will
find it useful.
- Notes from the calibration team meeting in Washington, DC,
Nov 29 - Dec 2, 2006.
Flatfielding chapter for Calibration Volumes
(last changes June 22, 2006)
The Journey of a photon through SNAP
(orig Mar 25, 2006, revised Apr 6, 2006).
A whimisical view of overall calibration,
as we watch a photon pass through the
obstacles in the SNAP telescope and detectors.
Determining filter parameters by observing stars (Jan 5, 2006)
Mike Lampton did all the work -- see his document
Filter parameters using stars alone?
which was last updated Oct 31, 2003.
I just added some explanatory text and changed the format.
Post-launch observations required to characterize flatfields
(Dec 22, 2005).
A rough calculation of number of photons from LEDs reaching focal plane
(Aug 18, 2005).
This first preliminary version may be superceded in the future.
Quantitative consequences of zero-point errors in SNAP photometry
(June 7, 2005). A talk given at the
2005 SNAP Collaboration meeting.
Volume 3 ("Flatfielding") of the SNAP Calibrations document
(May 16, 2005 -- first cut of section on dithering is now finished).
There is also a
Changes to CCD sensitivity in space
(Mar 20, 2005)
Zero-point errors in SNAP photometry and their effect on cosmology
(Feb 10, 2005)
Variations in PSF across an S2KB image
(Dec 11, 2004). Supports Nick Mostek's analysis
of photometry with the WIYN S2KB camera.
Using a free-flying spacecraft to calibrate standard stars (III)
(Nov 3, 2004). Replaced vague statements
with signal-to-noise calculations for a range of parameters.
Using a free-flying spacecraft to calibrate standard stars (II)
(Nov 2, 2004). A revised version,
based on many comments from calibration team members.
Using a free-flying spacecraft to calibrate standard stars
(Oct 28, 2004). A very rough outline of
the issues involved.
Semi-realistic tests of chip-to-chip offsets
(Aug 26, 2004). Tests of chip-to-chip offsets with
realistic stellar catalog and a grid of 10-second exposures.
How to recognize the various "flatfield" effects in SNAP data
(Aug 20, 2004). Describes the observations one must make
to recognize the signature of each sort of error.
A simple pipeline for simulating SNAP photometric measurements, v 0.2
(Aug 19, 2004).
Major additions: option for including noise in output magnitudes,
option to give each chip variation in sensitivity across its area.
Factors affecting chip-to-chip offsets
(Aug 10, 2004).
A simple pipeline for simulating SNAP photometric measurements
(Aug 01, 2004). The first release of the SNAP pipeline code.
Signal-to-noise calculations including sky, readnoise and dark current
(revised July 30, 2004).
Includes values for the exposure time
at which readout noise yields to noise from the sky background.
Flatfielding: theory and (current) practice
(FNAL calibration workshop, July 2004)
Photons per second for stars of magnitude V=20
some results from my photometric simulator
SNAP passbands: design and actual
Collaboration meeting: May 19, 2004
Three important factors in "flatfielding"
Collaboration meeting: May 19, 2004
Revised values for signals from stars and sky
(Apr 23, 2004)
Electron count rates in SNAP images
(Apr 15, 2004)
the revised calculations instead.
Status report on simulation progress
(Apr 01, 2004)
General plan and timescale for making a SNAP flatfield
(Mar 15, 2004)
Mathematical description of the photometric equation
(Oct 22, 2003)
Effect of fractional shifts in passbands on stars and SNe
(Sep 18, 2003)
Adding errors in filter transmission curves to simulation
(Sep 09, 2003)
Changes in instrumental magnitude as a function of incidence angle
for stars of various spectral types. There are only a set of
graphs, no text.
(Sep 04, 2003)
Improvements to the simulator design
(Aug 28, 2003)
Basic design of the photometric simulation
(Aug 21, 2003)
Results from WIYN 0.9m observations of Old SNAP Northern Field
(June 3, 2003)
Proposal to use the WIYN 0.9m Telescope to study the SNAP field
(May 17, 2003)
Some stellar statistics in the SNAP field
(May 12, 2003)
Location of the SNAP field
(May 2, 2003)
KIII Giants: Preliminary Results from a WIYN 0.9m Survey
with Nick Mostek.
Collaboration meeting: Mar 26, 2003
Using SNAP itself to span many magnitudes
(Sep 19, 2002)
Correcting instrumental magnitudes from SNAP
(Aug 23, 2002)
Errors in transferring the SNAP calibration to faint stars
(Mar 28, 2002)
Issues in Calibrating SNAP
Collaboration meeting: Feb 8, 2002
Step-by-Step procedure for transferring SNAP calibration
(Jan 31, 2002)
Spectra of Primary Calibration Stars for SNAP
(Oct 25, 2001)
Presentation on SNAP for the Astronomical Society of New York
(Oct 19, 2001)
Primary Calibration Stars for SNAP
(Oct 10, 2001)
Calibration of SNAP Standard Stars
(Jul 27, 2001)
Other SNAP resources
Last modified Oct 29, 2008 by MWR