Abstract: A practical stationkeeping method and apparatus wherein an electric propulsion system on a satellite is used to correct north-south drift and the majority of east-west drift which is caused by orbital eccentricity growth. A chemical propulsion system on the satellite is used to correct the remainder of east-west drift due to the growth of orbital semimajor axis. The method and apparatus eliminate the need for additional electric thruster burns in case of an electric thruster failure and therefore eliminates associated power and mass penalties.

Abstract: A method and system is disclosed for imaging a celestial object, typically the Earth, with a spacecraft orbiting the celestial object. The method includes steps of (a) operating an imager instrument aboard the spacecraft to generate data representing an image of the celestial object; (b) processing the image data to derive the location of at least one predetermined landmark in the image and a location of edges of the celestial object in the image; and (c) further processing the detected locations to obtain the attitude of the imager instrument. The method includes a further step of outputting the image and the imager instrument attitude to at least one end-user of the image, and/or using the imager instrument attitude to revise the image before outputting the image to the at least one end-user of the image. The generated data preferably represents a one half frame image, and the steps of processing and further processing thus occur at a one half frame rate.

Abstract: Solid core particles encapsulated in a single coat of paraffin wax, the wax having a melting point of about 40.degree. to about 50.degree. C. and a solids content of from 100 to about 35% at 40.degree. C. and from 0 to about 15% at 50.degree. C. The paraffin coat may comprise 20 to 90% by weight of the particle and may be from 100 to 1,500 microns thick. The coat prolongs the time in which particles encapsulated therewith may remain active in aqueous environments.The encapsulated particle is made by spraying molten wax onto the particles in a fluidized bed. Liquid or powder cleaning compositions, particularly automatic dishwashing liquid detergents, may incorporate 0.01 to 20% by weight of the composition of the coated wax-encapsulated particles.

Abstract: Solid core particles encapsulated in a single coat of paraffin wax, the wax having a melting point of about 40.degree. to about 50.degree. C. and a solids content of from 100 to about 35% at 40.degree. C. and from 0 to about 15% at 50.degree. C. The paraffin coat may comprise 20 to 90% by weight of the particle and may be from 100 to 1,500 microns thick. The coat prolongs the time in which particles encapsulated therewith may remain active in aqueous environments.The encapsulated particle is made by spraying molten wax onto the particles in a fluidized bed. Liquid or powder cleaning compositions, particularly automatic dishwashing liquid detergents, may incorporate 0.01 to 20% by weight of the composition of the coated wax-encapsulated particles.

Abstract: Solid core particles encapsulated in a single coat of paraffin wax, the wax having a melting point of about 40.degree. to about 50.degree. C. and a solids content of from 100 to about 35% at 40.degree. C. and from 0 to about 15% at 50.degree. C. The paraffin coat may comprise 20 to 90% by weight of the particle and may be from 100 to 1,500 microns thick. The coat prolongs the time in which particles encapsulated therewith may remain active in aqueous environments.The encapsulated particle is made by spraying molten wax onto the particles in a fluidized bed. Liquid or powder cleaning compositions, particularly automatic dishwashing liquid detergents, may incorporate 0.01 to 20% by weight of the composition of the coated wax-encapsulated particles.

Abstract: Stars are sensed by one or more instruments (1, 2) on board a three-axis stabilized satellite, for purposes of assisting in image navigation. A star acquistion computer (64), which may be located on the earth, commands the instrument mirror (33, 32) to slew just outside the limb of the earth or other celestial body around which the satellite is orbiting, to look for stars that have been cataloged in a star map stored within the computer (64). The instrument (1, 2) is commanded to dwell for a period of time equal to a star search window time, plus the maximum time the instrument (1, 2) takes to complete a current scan, plus the maximum time it takes for the mirror (33, 32) to slew to the star. When the satellite is first placed in orbit, and following first stationkeeping and eclipse, a special operation is performed in which the star-seeking instrument (1, 2) FOV is broadened.

Abstract: A system for achieving spacecraft camera (1, 2) image registration comprises a portion external to the spacecraft and an image motion compensation system (IMCS) portion onboard the spacecraft. Within the IMCS, a computer (38) calculates an image registration compensation signal (60) which is sent to the scan control loops (84, 88, 94, 98) of the onboard cameras (1, 2). At the location external to the spacecraft, the long-term orbital and attitude perturbations on the spacecraft are modeled. Coefficients (K, A) from this model are periodically sent to the onboard computer (38) by means of a command unit (39). The coefficients (K, A) take into account observations of stars and landmarks made by the spacecraft cameras (1, 2) themselves.

Abstract: Pixels within a satellite camera (1, 2) image are precisely located in terms of latitude and longitude on a celestial body, such as the earth, being imaged. A computer (60) on the earth generates models (40, 50) of the satellite's orbit and attitude, respectively. The orbit model (40) is generated from measurements of stars and landmarks taken by the camera (1, 2), and by range data. The orbit model (40) is an expression of the satellite's latitude and longitude at the subsatellite point, and of the altitude of the satellite, as a function of time, using as coefficients (K) the six Keplerian elements at epoch. The attitude model (50) is based upon star measurements taken by each camera (1, 2). The attitude model (50) is a set of expressions for the deviations in a set of mutually orthogonal reference optical axes (x, y, z) as a function of time, for each camera (1, 2). Measured data is fit into the models (40, 50) using a walking least squares fit algorithm.