Abstract: A method for controlling a geosynchronous spacecraft. A yaw axis and a roll axis of the spacecraft are oriented parallel to the earth equatorial plane. A coordinate frame of a payload is rotated about a minus roll axis of the spacecraft at an angle equivalent to an orbit inclination of the spacecraft, thereby maintaining elements of a payload pointing toward a desired region on the earth. A spacecraft attitude is corrected to maintain the payload elements pointing at the desired region on the earth.

Abstract: In general, a constellation of spacecraft is used to broadcast to a particular region with high angles of view in order to reduce blockage or shadowing. A constellation of a plurality of spacecraft is placed in 24-hour orbits having inclination of about 55°, eccentricity of about 0.32, semi-major axis of about 42,000 km, longitude of the ascending node of about 43° East, argument of perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East. The preferred number of spacecraft ranges from three to six. In a particular application of Digital Audio Broadcast to Europe in some embodiments, the most populous cities are provided with service from no more than about 10° from vertical, and broadcast takes place when the spacecraft are above at least 35° North latitude. The broadcast power is reduced during those portions of the orbit in which the ground track lies in the Southern hemisphere.

Abstract: A method for maintaining three axis control of a geosynchronous spacecraft without body rate measurements using reaction wheel assemblies. Earth sensor assembly angle measurements are utilized for high-bandwidth roll and pitch control. A positive pitch momentum bias is stored in the reaction wheel assemblies. A gyroscopic feedforward torque is applied to rotate reaction wheel assembly momentum in a yaw/roll plane of the spacecraft at orbit rate. A dynamic mode that couples yaw and roll axes and that results from applying the gyroscopic feedforward torque and the high-bandwidth roll control is damped based on earth sensor assembly roll measurements.

Abstract: A method for controlling spacecraft velocity. A thruster torque gimbal angle command is calculated to provide a desired thruster torque demand command including a desired momentum adjust torque and a desired attitude control torque. A velocity change error between a commanded velocity change and an actual velocity change, a commanded force vector based on the error to cause the actual velocity change to approach a commanded velocity change, and force gimbal angle commands and force thrust commands to achieve the commanded force vector are calculated; and/or an error between gimbal angles and thrust levels and reference gimbal angles and thrust levels, reference gimbal angle commands and reference thrust commands to drive actual gimbal angles and thrust levels toward reference gimbal angles and reference thrust levels are calculated. A total gimbal angle command is calculated by adding the torque gimbal command with at least one of the force gimbal angle command and the reference gimbal angle command.

Abstract: A device and method provide improved measurement of flow through an enclosed channel, such as a pipe. A flow measurement device, such as a differential pressure sensing pitot tube, includes a pressure sensing probe that is inserted into the pipe for measuring the rate of fluid flow therein. A compressible or elastic barrier is attached to the distal end of the sensing probe to fill the space between the tip end of the sensing probe and the nearby portion of the inside wall of the fluid carrying pipe. The resilient barrier prevents undesirable fluid flow between the tip end of the sensing probe and the inside wall of the pipe.

Abstract: A three-axis stabilized spacecraft is subject to a velocity change in a desired direction by a thruster. Unavoidable alignment errors cause a body torque, which tends to slew the body away from the attitude which orients the thrust axis in the direction. The attitude control system eventually corrects the attitude, but the thrust during the attitude transient results in an error in the direction of the velocity change. This error in the direction accumulates during the attitude transient. When the attitude transient passes, no further pointing error occurs. A control system, operating without an accelerometer, determines the total error accumulated during the attitude transient, and processes the error signal to generate a supplemental torque demand signal, which is added to the torque demand signal produced by the attitude control system, to cause an oppositely-directed attitude transient to thereby cancel the original velocity change direction error.

Abstract: A spacecraft (10) carries a solar panel (17) which rotates to follow the sun, and also carries various thrusters (20). Thruster plume impingement on the solar panel affects the torque applied to the spacecraft body (12) in a manner which depends upon solar panel angle. The errors in the thrust during stationkeeping tend to perturb attitude, especially early in the maneuver, because of the delay inherent in the attitude control loop. A torque bias is summed with the residual torque demand signal to correct for the errors in torque. The torque bias signal is generated by a Fourier model of the torques, updated by an adaptive tuning filter, so that successive stationkeeping maneuvers progressively adapt the amplitude and phase of the Fourier coefficients in a manner which tends to minimize the residual torque demand and attitude error. Thus, the torque bias signal automatically approaches the correct value.

Abstract: A spacecraft (10) has an attitude sensor (20) mounted on its body (12). The sensor must be maintained near a temperature setpoint. Each sensor (20) produces its own temperature-indicative signal. Each attitude sensor is coupled to a thermally conductive instrument platform (18). A standoff (21) supports the platform (18) away from a baseplate (16) and the spacecraft body (12). The standoff (21) includes a thermally conductive portion (22) adjacent the platform (18), and a nonconductive portion (24) remote from the platform. An electric heater (26) is connected to the thermally conductive portion (22) of the standoff (21). A temperature sensor (28) thermally coupled to the platform (18) generates platform temperature signals. A filter (212) high-pass filters either the platform temperature signals or the attitude sensor temperature signals, to form filtered signals. A combining circuit (218) combines the filtered signals with the other temperature signals, to make composite temperature signals.

Abstract: A spacecraft includes a three-axis attitude control system. When velocity change thrusters are fired, their plumes impinge on a solar array, at angles which vary with the solar array position. This causes disturbance torques which vary with the solar array position. Disturbance torque information signals or torque bias signals which depend upon the solar array angle are summed with the torque demand signals which control the attitude control system during firing of the velocity change thrusters, to modify the attitude correction torques. The bias torque signals are generated by a Fourier processor based upon stored Fourier coefficients together with signals from a solar array angular position sensor.

Abstract: A three-axis stabilized spacecraft includes a plurality of primary attitude control thrusters, the torque vectors of which lie in, or parallel to a primary plane. It also includes at least two more secondary attitude control thrusters, the torque vectors of which lie in a secondary plane which is not parallel to the primary plane. The control system produces attitude error signals, which are processed with a PID characteristic to produce impulse demand signals, all in known fashion. The impulse demand signals are transformed into an auxiliary coordinate system, in which two of the three auxiliary axes lie in the primary plane, and the third is orthogonal thereto. One of the secondary thrusters is selected, which has, along the third auxiliary axis, the largest torque magnitude and the same sign as the transformed impulse demand.

Abstract: A method for protecting synthetic and natural fibres against phototendering. The method comprises treating the fibres with a substituted benzotriazolesulfonate of the following formula: ##STR1## wherein (I) R.sub.1 is hydrogen or halogen, R.sub.2 is hydrogen or alkyl, R.sub.3 is hydrogen or hydroxy, R.sub.4 is --SO.sub.3 X where X is hydrogen or an alkali metal, and R.sub.5 is hydrogen, with the proviso that R.sub.2 is not methyl when R.sub.1 and R.sub.3 are hydrogen; or(II) R.sub.1, R.sub.3 and R.sub.4 are hydrogen, R.sub.2 is --SO.sub.3 X where X is hydrogen or an alkali metal, and R.sub.5 is --OR.sub.6 where R.sub.6 is hydrogen or alkyl; or(III) R.sub.1 is hydrogen or halogen, R.sub.2 is --SO.sub.3 X where X is hydrogen or an alkali metal, R.sub.3 and R.sub.5 are hydrogen, and R.sub.4 is hydrogen, alkyl or benzyl; or(IV) R.sub.1 is --SO.sub.3 X where X is hydrogen or an alkali metal, R.sub.2 is alkyl, R.sub.3 and R.sub.5 are hydrogen, and R.sub.4 is hydrogen or alkyl;under acidic conditions.

Abstract: A method for protecting proteinaceous fibres, either dyed or in their natural form, against photodegradation and thermal degradation. The method comprises treating the fibres with a sulfonated s-triazine derivative of formula (I), wherein R.sup.1 is hydrogen, alkyl, hydroxyl, O-alky, OOC-alkyl or OOCNH-alkyl; R.sup.2 is hydrogen, alkyl or SO.sub.3 X; R.sup.3 is aryl, substituted aryl or O-alkyl; and X is hydrogen, NH.sub.4 or alkali metal, or formula (II), wherein R.sup.1 and R.sub.4 are hydrogen, alkyl, hydroxyl, O-alkyl, OCC-alkyl or OOCNH-alkyl; R.sup.2 and R.sup.5 are hydrogen, alkyl or --SO.sub.3 X; R.sup.3 is hydrogen or --SO.sub.3 X; R.sup.6 is aryl, substituted aryl, O-alkyl or O-aryl; and X is hydrogen, NH.sub.4 or alkali metal; under acidic conditions. The method is particularly suitable for treating dyed and undyed wool, silk, mohair and cashmere fibers, including blends thereof.

Abstract: A method for protecting synthetic and natural fibres against phototendering. The method comprises treating the fibres with a substituted benzotriazolesulfonate of the following formula: ##STR1## wherein (I) R.sub.1 is hydrogen or halogen, R.sub.2 is hydrogen or alkyl, R.sub.3 is hydrogen or hydroxy, R.sub.4 is --SO.sub.3 X where X is hydrogen or an alkali metal, and R.sub.5 is hydrogen, with the proviso that R.sub.2 is not methyl when R.sub.1 and R.sub.3 are hydrogen; or(II) R.sub.1, R.sub.3 and R.sub.4 are hydrogen, R.sub.2 is --SO.sub.3 X where X is hydrogen or an alkali metal, and R.sub.5 is --OR.sub.6 where R.sub.6 is hydrogen or alkyl; or(III) R.sub.1 is hydrogen or halogen, R.sub.2 is --SO.sub.3 X where X is hydrogen or an alkali metal, R.sub.3 and R.sub.5 are hydrogen, and R.sub.4 is hydrogen, alkyl or benzyl; or(IV) R.sub.1 is --SO.sub.3 X where X is hydrogen or an alkali metal, R.sub.2 is alkyl, R.sub.3 and R.sub.5 are hydrogen, and R.sub.4 is hydrogen or alkyl;under acidic conditions.

Abstract: A dual bandwidth loop filter includes a filter loop, resistive means, switching means for coupling and decoupling the resistive means for changing the bandwidth of the loop from a wider acquisition bandwidth to a narrower tracking bandwidth and a sweep generator for enabling the filter to provide sweep acquisition of an incoming signal.