Hydrolysis rate constants for 18 chlorinated methanes, ethanes, ethenes, and propanes have been measured in dilute aqueous solutions within the temperature range of 0-180 "C and at pH values of 3-14. Arrhenius parameters were determined for both neutral and alkaline hydrolysis reactions. Reactivity of these compounds in basic solutions increases in accord with the expected acidity of the most reactive hydrogen atom in the molecule. Neutral hydrolysis appears to depend on both the C-Cl bond strength and the degree of steric hindrance a t the reaction site. Only a neutral hydrolysis process occurs for CC14, l,l,ltrichloroethane, and 2,2-dichloropropane. The chlorinated ethenes and hexachloroethane react only with hydroxide under severe conditions and exhibit no neutral hydrolysis. Some of these compounds eliminate HCl, whereas others substitute OH for C1 to form alcohols that may react further to give aldehydes or carboxylic acids as products. Environmental hydrolysis half-lives (25 OC, pH 7) range from 36 h for 2,2-dichloropropane to 1850 years for CHC13 and to over lo6 years for C&16 and the ethenes.

Methodology and results for the Global Positioning System based attitude determination of a gravity gradient stabilized satellite are presented. Algorithms for on-orbit antenna baseline estimation, attitude initialization, point solution, and Kalman filtering are described. These algorithms are demonstrated using flight data collected on board the U.S. Air Force RADCAL Satellite. The precision of the final attitude estimates is assessed to be at the level of 0.4 deg for pitch and roll and 0.7 deg for yaw. B b C e H I /1./2./3 lA,JA,kA k L v x x z ft Ar 8q S(p <$(•) v 0 Nomenclature = body frame = baseline vector = transformation matrix from orbit local to body frame = line of sight unit vector : measurement gradient matrix : identity matrix ; principal moments of inertia : basis vectors for coordinate frame A • integer cycle = orbit local frame = four-element attitude quaternion from orbit local to body frame = cross product matrix associated with the vector v; 0 v 3 -v 2Ṽ x = 0 0: state vector : measurement residual vector : line bias range difference : measured phase difference = three-element correction quaternion = phase difference residual : estimation error of a given quantity = phase difference measurement error = spacecraft orbital rate : inertial angular velocity of the body in body coordinates : local angular velocity of the body = vector quantity expressed in coordinate frame A • estimate of a quantity = quaternion composition operation; see Ref. 1

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This paper describes a methodology for combining attitude and baseline estimation into one comprehensive filter. The nominal filter states include attitude quaternion errors, angular velocity errors, and baseline errors. Previous approaches have relied on determining accurate baselines first and then using those baselines for attitude estimation. The method presented here combines these two steps into one algorithm. The advantage is that baseline calibration can be performed while simultaneously producing attitude information. In addition, the combined filter allows for baseline flexure, whereas previous approaches are based on the assumption of fixed baselines. This algorithm works best when attitude motion is present and when a good dynamic model is available. Results from simulated data as well as flight data are presented.

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