Two reports describe a Rayleigh-scattering attitude sensor (RSAS) - an optoelectronic instrument for determining the orientation of a spacecraft. An RSAS comprises a telescope/video-camera/image-digitizer combination that is mounted on the spacecraft and that captures images of the limb of the Earth in 355-nm-wavelength sunlight that has been Rayleigh-scattered from the atmosphere. (At 355 nm, the atmosphere scatters strongly but does not absorb significantly.) A computational model of the 355-nm radiance of the atmosphere as a function of altitude, lighting conditions, and viewing angle is then used to extract, from the image data, an estimate of the angle between the line of sight of the RSAS and the nadir.

This work was done by Pawan K. Bhartia and Ernest Hilsenrath of Goddard Space Flight Center.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

the Patent Counsel
Goddard Space Flight Center; (301) 286-7351

Refer to GSC-13858