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The Dawn of RISE (1Dec92)
(from NSO, NOAO Newsletter No. 32, 1 December 1992)

Measurement and understanding of the Sun's variable outputs poses one
of the most important problems in solar research. In 1987 and 1989, two
workshops were held at the National Center for Atmospheric Research and
the National Solar Observatory to discuss progress in measurement and
understanding of the Sun's radiative outputs, of stellar light
variations, and of their impact on studies of the Earth's climate and
atmospheric chemistry. The report of the working groups formed at the
first workshop entitled RISE, Radiative Inputs of the Sun to Earth laid
out a systematic research program for the 1990s aimed at increasing our
knowledge in this area.

In September 1991 a proposal was prepared by the RISE/PSPT Scientific
Advisory Committee and submitted by NSO to the National Science
Foundation aimed at creating a network of precision solar photometric
telescopes (PSPT) as outlined in the RISE plan. The proposed
instruments will obtain high precision measurements of continuum images
of the Sun, as well as measurements in the core of the Ca II K line.
These measurements will yield important data on the diminution of the
total irradiance of the Sun by sunspots as well as the enhancement of
this irradiance by faculae and the distribution and strength of plages
and network in the chromosphere.

The NSF Division of Atmospheric Sciences has provided NSO with some
seed funding to initiate the first steps toward the RISE program. In
anticipation of the creation of the PSPT network and to gain some
operational experience, data will be taken with the NSO/Kitt Peak
Vacuum Telescope and High-Degree Helioseismometer. The High-Degree
Helioseismometer was developed jointly by NSO, Bartol Research
Institute, and NASA/GSFC. The instrument was designed to take precision
Ca II K line full-disk images of the Sun to study solar oscillations.
It was operated for nearly three months at the South Pole in the
austral summer of 1990-1991.

The instrument has now been mounted on top of the NSO/Kitt Peak Vacuum
Telescope where it is fed by the same coelostat that feeds the
telescope and may be operated simultaneously. The NSO/Kitt Peak Vacuum
Telescope synoptic observers will attempt observations with this
instrument once per day during the normal synoptic program. The
observations will be a few integrations per minute, with ten minutes of
such one-minute integrations being recorded in order to suppress the 5
minute oscillation. Darks and flats will be taken for each observing
sequence.

An REU-funded student in Tucson will process the data recorded on
Exabyte tapes weekly. Processing will consist of correction for dark
and flat, and integration of the 10 minutes of corrected images.
Scattered light and smearing determination using the Toner-Jefferies
algorithm may be done if practical. Deconvolution of the scattered
light and smearing may also be attempted using the Jefferies iterative
deconvolution. Both corrected and deconvolved images will be binned
into multidimensional histograms. The dimensions will include distance
from disk center and coarse latitude and meridian distance. The
resulting data cube will be such that summing can be done in any and
all dimensions to get a meaningful result. It may prove useful to
compute image excess and deficit indices relative to the mean disk. An
archive of all the data will be maintained on Exabyte tapes (and
possibly CD-ROMs).

A few of the most recent images will be kept in a circular buffer on an
anonymous FTP disk to enable access by anyone. Daily indices derived
from the images will be kept as an ASCII data file on the same disk. A
mail server will distribute recent indices to those in the community
who query a special mail address. This small project should provide
good experience for the RISE/PSPT program as well as establish a data
base useful to a wide range of researchers.

Jack Harvey, Jeremy Wagner

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