Recent results on zodiacal light are used to show that optics, dynamics, and infrared must be considered together to properly and fully characterize the interplanetary dust complex.

Color photographs of the inner Zodiacal Light were obtained aboard Saliout 7 with Kodak Ekta 400. Absolute calibrations were performed in-Flight with attenuated Sun light. The photometric analysis was carried out in three colors and corrections were introduced for the 01 emission of the F layers. The brightness of the Zodiacal Light along the ecliptic is found in good agreement with published data while its color is found slightly redder than the Sun. Its out-of-ecliptic variation coincides neither with the fan nor the ellipsoidal model; the photometric axis is found near the projection of the orbital plane of Venus.

Ground-based observations of the evening zodiacal light taken by Weinberg and Mann from Mt. Haleakala, Hawaii, during March 1966 are used to derive a table of zodiacal light brightnesses at high spatial resolution (as little as 0.5° in differential ecliptic longitude λ−λ⊙ and 1.0° in ecliptic latitude β) over the region 29. 5°< λ−λ⊙ < 56°, −30°< β <30°. Significant differences are found in the brightness distributions above and below the ecliptic plane.

The reduction method and the results of a photoelectric surface photometry of the Zodiacal Light at a wavelength of 555 nm are presented. A comparison with published results is also given.

Background starlight observed by the Pioneer 10 Imaging Photopolarimeter from beyond the asteroid belt is used to isolate zodiacal light in Pioneer observations at heliocentric distances R between 1 and 3 AU. Near-ecliptic zodiacal light brightness data in the range 65° to 180° elongation ε are used to depict changes in the shape of the zodiacal light with ε and R and are compared to the corresponding views seen from the Earth and from the Helios 1 and 2 spacecraft.

Results from photometers on board the D2B satellite (1975) for the whole sky in ultraviolet and blue light, are combined to generate a very well defined empirical representation of the zodiacal light and Gegenschein. The sky background is then obtained by subtraction of this model from the data.

Observations of the spectrum of the zodiacal light in the wavelength range 1800-3000 Å have been obtained in two recent sounding rocket experiments. The September 1979 observation was made close to the ecliptic plane at elongation angles of 20° and 28° and with a spectral resolution of 25 Å, while in April 1981 the elongation was 125° (inclination 60°), and the spectral resolution 50 Å. Both observations confirm the slight reddening in the ultraviolet reported previously and show the same dependence on elongation as in the visible. There appears to be some structure in the ultraviolet albedo of the dust grains near 2800 Å but the exact nature of this structure cannot be determined at the low spectral resolution of the present observations. Detailed descriptions of the two observations has been given by Cebula and Feldman (1982) and Tennyson (1983), respectively.

Gegenschein observations from Pioneer 10 were found to have brightness structures with an amplitude of about 10% and a period of several to ten degrees in elongation. A search is made for such structures in high angular resolution ground-based observations from Mt. Haleakala, Hawaii. A new empirical method is used to correct for atmosphere-originated radiation. Background starlight is subtracted using Pioneer 10 observations from beyond the asteroid belt. Preliminary analysis of the ground data also indicates the presence of small amplitude structures in the brightness distribution.

Large-scale interplanetary dust arcs were predicted by Schuerman (1980) to be associated with the planets. An arc, if one exists, would produce asymmetries on opposite sides of the Gegenschein during the Earth’s two passages through the arc each year. A brief description is given of Gegenschein/arc observing constraints, of future viewing opportunities, and of the results of a test program conducted from Mt. Haleakala, Hawaii, in Jan/Feb 1984 when the Earth encountered the arc associated with Saturn.

The Infrared Astronomical Satellite (IRAS) has completed a sensitive, highly redundant survey of the full sky in four broad photometric bands at 12, 25, 60, and 100 micrometers wavelength. The survey measured interplanetary dust emission over elongation angles ranging from 60 to 120 degrees. Bright emission from the main cloud is consistent with optically thin blackbody emission. The grains are evidently quite black, with an “apparent albedo” of about 0.07. The data show clear evidence for deviation of the dust symmetry surface from the ecliptic plane. Surprising bands of emission were discovered near the ecliptic plane and about ten degrees on either side of it. The heliocentric distance of this material, suggested to be asteroidal in origin, is inferred to be about 2.5 AU from both color temperature and parallax measurements.

A balloon observation of the F-corona in visual and infrared regions was carried out by Japanese and Indonesian teams at the total solar eclipse on June 11, 1983, in Java, Indonesia. For the visual observation, a SIT television camera, with 4 interference filters (5300Å, 6000Å, 7200Å and 8000Å) and a 45°-step rotating polarizer, was used. The camera measured brightness distributions in a sky area of 5°×5° centered at the eclipsed sun at each polarizer position for each filter. In this paper, a part of results, which are the brightness and polarization distributions in a half area of the 6000Å picture, is shown.

During the totality on June 11, 1983 in East Java, Indonesia, a near infrared photometric observation of the solar corona was made using a stratospheric balloon, which was successfully launched by a joint team of ISAS, Japan and LAPAN, Indonesia. The surface brightness distributions in four near infrared bands: at 1.25, 1.65, 2.25 and 2.8 μm, have been obtained in the outer coronal region. Noticeable excess emissions superposed on the strong coronal background emission have been recorded in the scan profiles at 1.25 and 1.65 μm, and less conspicuously at 2.25 μm as well, at about 4 R⊙ from the sun. From the observed spectral and spatial characteristics, the excess emission component appears to originate in the thermal radiation from the circumsolar dust ring made of relatively large particles of about 100 μm in radius and with the olivine-like optical properties.

Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grain alone. Preliminary analysis on the recent infrared data of F-corona by Maihara et al.(1984) has suggested that the ring particle has different physical properties compared with the dust grains, which produce the background F-corona.

This review deals with the main properties of the F-corona. Analysis of its morphology and photometry allows to derive a new axisymmetric, non-spherical model. Polarization, color and infra-red properties are further considered. We suggest the existence of a variable “local” component surperimposed on a quasi-stationnary “far” component.

The radial velocities of F-corona for total eclipse July 31, 1981 obtained at elongations (3-7) R⊙ are interpretated assuming prograde motion in circular Keplerian orbits of circumsolar dust. In computations isotropic plus diffraction scattering functions are used. In supposition of silicate grains the best coincidence with observations is received for grains with radii about 0.4 μm with the presence of dust free zone (d.f.z.) around the Sun to heliocentric distances (6.5-14) R⊙ and high grain concentration at the edge of this dust free region.

The presence of negative radial component of radial velocities can be explained by falling of the matter into the Sun under influence of Poynting-Robertson effect of solar wind for porous grains with radii less than 0.4 μm . The effect of radiation drag for these small grains is essentially less. Using grains with radii less than 0.4 μm the sizes of which decrease as approaching to the Sun one may explain the inner F-corona brightness.