Data Set Overview
  =================
    This data set includes calibration observations of those stars observed by
    the Hayabusa spacecraft with the AMICA instrument during the cruise phase
    of the mission.  The calibration has been done with respect to the Eight
    Color Asteroid System (Tedesco et al. 1982) because the filters chosen for
    the camera (Nakamura et al. 2001) are similar to those used for the Eight
    Color Asteroid Survey (Zellner et al. 1984).
 
    The observations were made on 2008 June 15, 17, 18, and 19 UT from
    Goodricke-Pigott Observatory near Tucson, Arizona (east longitude 248.918
    deg, north latitude 32.155 deg, elevation 2452 feet).  Sky conditions were
    generally photometric, with occasional small and isolated cumulus clouds
    drifting through the sky.  Overhead power lines did occasionally corrupt
    an exposure, but care was taken to remove affected measures from the
    averages.  Tree branches low in the northwestern sky set an upper limit on
    the airmass used for the atmospheric extinction determination.
 
    The telescope was an Orion Astroview 120ST EQ 120 mm aperture f/5
    refractor, but mounted on a Vixen 'Great Polaris Deluxe' high precision
    equatorial mount and tripod instead of the standard mount. The mounting
    was equipped with the Vixen 'Sky Sensor 2000' computer hand paddle and
    motor drive system which provided tracking and Go-To capability.  The
    image scale was 6.88 arseconds per pixel and the field of view was 3521
    arcseconds.  The aperture was reduced to approximately 25 mm by placing a
    perforated sheet of aluminum foil over the telescope's objective lens,
    reducing the amount of light uniformly at all wavelengths.  The aluminum
    sheet reduced the aperture to about 1 inch.  The small aperture was
    necessary to avoid detector saturation on the brightest stars with the
    shortest available exposure times (0.12 sec).  The small aperture caused
    scintillation noise to be the dominant source of the photometric error for
    the bright stars.
 
    The camera was a Santa Barbara Instrument Group ST-9E camera with parallel
    port interface and 5-position CFW-8 color filter wheel. The camera has a
    front-side illuminated 512x512 Kodak KAF0261E CCD with 20 micron square
    pixels and peak quantum efficiency of about 67 percent around 0.59
    microns. Thermoelectric cooling permits operation at about 30 C below
    ambient temperature.  The ambient temperature tended to be near 40 C
    around sunset and around 20 C before sunrise.  Although the AMICA filter
    set included u-long and z-short filters, the use of these filters by
    Hayabusa was severely limited by the failed gyros because of the longer
    exposures required.  Calibration of these filters would have been
    similarly difficult due to their low throughput, and because the filter
    wheel could not accommodate all seven filters simultaneously anyway, the
    decision was made to limit the calibration work to just the bvwxp subset
    of filters.
 
    The observer was David J. Tholen, with some initial assistance from Roy A.
    Tucker.  The photometric reductions were performed primarily by Marco
    Micheli under the supervision of Tholen.
 
    The bright stars were observed in groups of ten exposures through each
    filter, with the standard deviation in the ten measurements representing
    the uncertainty assigned to the instrumental magnitude.  As noted above,
    scintillation noise was the dominant source of phootmetric error.  The
    filters were generally cycled through in the order vbwxpv, with the
    repetition of the v filter intended to be a test of photometric
    conditions. On one night, the filter wheel became stuck, and a spare wheel
    was used in its place, with all filters transferred to the spare wheel in
    the exact same order and location relative to the fiducial.  Nevertheless,
    after observations recommenced, it was discovered that the association
    between filter wheel position and filter had changed, causing the filter
    recorded in the FITS headers to be wrong.  We had to rely on the
    handwritten logs for this night to reconstruct the actual filters.  Before
    the problem was discovered, a few observations were unintentionally made
    with the w filter being repeated at the beginning and end of the sequence.
 
    Standard stars were selected from the Eight Color Asteroid System (Tedesco
    et al. 1982) and included SA51, SA54, SA82, and Aquila.  The brightest
    stars in these regions are much fainter than the stars being calibrated,
    so it was necessary to take much longer exposures to achieve adequate
    signal-to-noise ratios.  However, exposures were limited to at most 120
    sec to avoid image degradation due to telescope tracking error, and were
    used when necessary (faint red star being observed through the b filter,
    or faint blue star being observed through the p filter, for example).
    Exposures were made in groups of four so that the standard deviation could
    provide an estimate of the photometric error.
 
    The midnight snack brownies were Betty Crocker fudge brownies with
    walnuts.  Number of brownies consumed was three per person initially,
    right out of the oven, but none remained of the one box prepared by the
    end of the observing.
 
    Nakamura, T., A. M. Nakamura, J. Saito, S. Sasaki, R. Nakamura, H. Demura,
    H. Akiyama, D. Tholen, and AMICA team 2001.  Multi-band imaging camera and
    its sciences for the Japanese near-earth asteroid mission MUSES-C.  Earth
    Planets Space 53, 1047-1063.
 
    Tedesco, E. F., D. J. Tholen, and B. Zellner 1982.  The eight-color
    asteroid survey: Standard stars.  Astron. J. 87, 1585-1592.
 
    Zellner, B., D. J. Tholen, and E. F. Tedesco 1985.  The eight-color
    asteroid survey: Results for 589 minor planets.  Icarus 61, 355-416.

Confidence Level Overview
  =========================
    Sky conditions
    ==============
 
    Sky conditions were generally photometric, with occasional small and
    isolated cumulus clouds drifting through the sky.  Overhead power lines
    did occasionally corrupt an exposure, but care was taken to remove
    affected measures from the averages.  Tree branches low in the
    northwestern sky set an upper limit on the airmass used for the
    atmospheric extinction determination.
 
    Aperture reduction
    ==================
 
    The telescope aperture was reduced to approximately 25 mm by placing a
    perforated sheet of aluminum foil over the telescope's objective lens.
    The small aperture was necessary to avoid detector saturation on the
    brightest stars with the shortest available exposure times (0.12 sec).
    The small aperture caused scintillation noise to be the dominant source of
    photometric error for the bright stars.
 
    Reduced filter set
    ==================
 
    Although the AMICA filter set included u-long and z-short filters, the use
    of these filters by Hayabusa was severely limited by the failed gyros
    because of the longer exposures required.  Calibration of these filters
    would have been similarly difficult due to their low throughput, and
    because the filter wheel could not accommodate all seven filters
    simultaneously anyway, the decision was made to limit the calibration work
    to just the bvwxp subset of filters.
 
    Stars Observed
    ==============
 
    Due to a miscommunication, the star eps Crv was included in this data set
    although it was not imaged by AMICA.  The stars alpha Ori, alpha Crv, and
    beta Tau were imaged by AMICA but were not included in the observations in
    this data set.
 
    Variability of Standards
    ========================
 
    Some of the standard stars used in this data set are or may be variable.
    Here is some additional information drawn from SIMBAD about the possible
    variability of the standards.  NSV is the New Catalog of Suspected
    Variables.
 
    31 Leo - a double star, but no known variability.
 
    alpha Leo - double star, listed in NSV as possibly variable with 0.07
    magnitude amplitude.
 
    eps Crv - Marked as variable on SIMBAD. The NSV catalog says
    it varies by 0.08 magnitudes, but the period and the type are not
    specified.
 
    beta Crv - Marked as variable on SIMBAD. The NSV catalog
    says it varies by 0.06 magnitudes, but the period and the type are
    not specified.
 
    alpha Vir - A well established variable, of beta Cep typ, pulsating
    every 4 days with 0.1 magnitudes amplitude.
 
    alpha Sco - A variable and double, long period irregular with amplitude up
    to 0.28 magnitudes.
 
    tau Sco - A single star, and apparently not variable.