3 research outputs found
Near-Limb Zeeman and Hanle Diagnostics
"Weak" magnetic-field diagnostics in faint objects near the bright solar disk
are discussed in terms of the level of non-object signatures, in particular, of
the stray light in telescopes. Calculated dependencies of the stray light
caused by diffraction at the 0.5-, 1.6-, and 4-meter entrance aperture are
presented. The requirements for micro-roughness of refractive and reflective
primary optics are compared. Several methods for reducing the stray light (the
Lyot coronagraphic technique, multiple stages of apodizing in the focal and
exit pupil planes, apodizing in the entrance aperture plane with a special
mask), and reducing the random and systematic errors are noted. An acceptable
level of stray light in telescopes is estimated for the V-profile recording
with a signal-to-noise ratio greater than three. Prospects for the limb
chromosphere magnetic measurements are indicated.Comment: 11 pages, 3 figure
JIRAM, the Jovian Infrared Auroral Mapper
JIRAM is an imager/spectrometer on board the Juno spacecraft bound for a polar orbit around Jupiter. JIRAM is composed of IR imager and spectrometer channels. Its scientific goals are to explore the Jovian aurorae and the planet's atmospheric structure, dynamics and composition. This paper explains the characteristics and functionalities of the instrument and reports on the results of ground calibrations. It discusses the main subsystems to the extent needed to understand how the instrument is sequenced and used, the purpose of the calibrations necessary to determine instrument performance, the process for generating the commanding sequences, the main elements of the observational strategy, and the format of the scientific data that JIRAM will produce
The Environment of Lyman- alpha Absorbers in the Sight Line toward 3C 273
We present new ground-based data following up on the HST discovery of
low-redshift Lya absorption in the sight-line to the quasar 3C273. Narrow-band
filter observations show that there are no H II regions within a 12 kpc radius
of the line-of-sight to the quasar, at the velocities of three of the
absorbers. Broad-band imaging shows that there are no dwarf galaxies at Virgo
distances with absolute magnitude above MB~-13.5 and within a radius of 40 kpc.
We present fiber spectroscopy of galaxies within a radius of 1 deg, down to an
apparent magnitude of B~19. We show that the absorbers are definitely not
distributed at random with respect to the galaxies, but also that the
absorber-galaxy correlation function is not as strong as the galaxy-galaxy
correlation function on large scales. Our data are consistent with the
hypothesis that all galaxies more luminous than 1/10 L* have effective
cross-sections (for association with absorbers with Log(NH)>13.0), of between
0.5 and 1 Mpc. We also show a clear case of a Lya absorber which has no galaxy
brighter than MB=-18 within a projected distance of 4.8 Mpc, and discuss the
possibility that Lya absorbers are destroyed in a rich galaxy environment.Comment: 36 pages, AAS LaTeX v3.0, (postscript version of paper, tables and 5
figures and 3 half-tones available by anon ftp) IOA-93-0