Apparatus which determines latitude and longitude from the deriuatives of two coordinates of a star

Claim 2

A navigational system responsive to light from a celestial body for providing outputs corresponding to longitude and latitude, comprising a telescope arranged to transmit an image of the celestial body, means connected to the telescope for driving the telescope so as to track the celestial body, a measuring circuit connected to the driving means for providing measurement signals corresponding to the zenith angle and the azimuth angle of the celestial body, signal means connected to the measuring circuit for providing signals corresponding to the rate of change of the azimuth angle and to the rate of change of the zenith angle in accordance with the signals from the measuring circuit, and means connected to the signal means for providing the longitude and latitude outputs in accordance with the signals from the signal means.

Claim 3

A navigational system of the kind described in claim 1 in which the output means includes means for providing a signal corresponding to Greenwich Sidereal Time G.S.T., means for providing a signal corresponding to the Right Ascension R.A. of the celestial body, means for providing a signal corresponding to the angle delta of declination of the celestial body, and computing means connected to the signal means, to the Greenwich Sidereal Time signal means, to the Right Ascension signal means and to the declination angle signal means for providing the outputs in accordance with the following equations: and East Longitude R.A. - G.S.T. + phi ; where lambda is the latitude angle, phi is the hour angle and d psi /dt is the rate of change of the azimuth angle, and d Nu /dt is the rate of change of the zenith angle.

Claim 4

A navigational system of the kind described in claim 2 in which the declination angle means includes two registers connected in series to the measuring circuit so that the registers store successive zenith angle measurement signals, a pulse source connected to the registers and providing an ''enter'' pulse train to the register connected to the measurement circuit for entering the measurement signal in that register periodically and a ''shift'' pulse train for shifting the contents of the registers periodically, an adder connected to the registers and providing a signal corresponding to the sum of the contents of the registers, and means connected to the adder for dividing the signal from the adder in half to provide a signal corresponding to the average zenith angle; and the computing means computes the angle delta of declination in accordance with the equation cos Nu cos lambda cos phi cos delta + sin lambda sin delta where Nu is the average zenith angle.

Claim 5

A navigational system of the kind described in claim 1 in which the telescope is controlled to periodically track the celestial body and each tracking of the celestial body occurs after the lapse of a predetermined time interval.

Claim 6

A navigational system of the kind described in claim 4 in which the signal means includes means connected to the measuring circuit for storing successive zenith angle measurement signals, subtracting means connected to the storing means for determining the difference between two successive zenith angle measurement signals to provide a signal corresponding to the rate of change of the zenith angle of the celestial body, the azimuth angle measurement signal corresponds to the rate of change of the azimuth angle, and means for delaying the azimuth angle measurement signal so that the average zenith angle signal, the rate of change of the zenith angle signal and the rate of change of the azimuth angle signal are for the same time period.

Claim 7

A navigational system of the kind described in claim 5 in which the storing means includes two registers connected to the pulse source and one register connecting the other regisTer to the up-down counter and the register connected to the up-down counter is periodically controlled by pulses from the pulse source to enter the count from counter and the contents of both registers are shifted periodically by shift pulse trains from the pulse source so that the registers contain successive counts.

Claim 8

A navigational system of the kind described in claim 4 in which the telescope provides an image of the celestial body and the driving means includes means responsive to the image of the celestial body for providing signals corresponding to the displacement of the image from a reference point, control means connected to the telescope and to the displacement signal means for periodically moving the telescope in response to the displacement signals so as to align the image of the celestial body with the reference point.

Claim 9

A navigational system of the kind described in claim 7 in which the control means includes means for providing a pulse train, means connected to the telescope for changing the position of the telescope in accordance with the displacement signals, switching means connected to the displacement signal means, to the pulse train means and to the positioning means for passing the displacement signals to the positioning means in response to the pulses in the pulse train and blocking the displacement signals during the absence of pulses in the pulse train.

Claim 10

A navigational system of the kind described in claim 7 in which the displacement signal means includes an image-dissector tube having a photocathode surface and arranged with the telescope so as to provide a signal when the image from the telescope is displaced on the photocathode surface of the image-dissector tube from the center of the photocathode surface in one sense and when the image on the photocathode surface is displaced from the center of the photocathode surface in another sense having a 90* spatial relationship to the first sense, and interpreting means connected to the image-dissector tube for providing the displacement signals in accordance with the signal from the image-dissector tube.

Claim 11

A navigational system of the kind described in claim 9 in which the control means includes means connected to the telescope for moving the telescope about a vertical axis in response to one displacement signal, means connected to the telescope for moving the telescope about a horizontal axis in response to the other displacement signal, means for providing a pulse train, and switching means connected to the horizontal axis moving means, to the vertical axis moving means, to the interpreting means and to the pulse train means for passing the one displacement signal to the vertical axis moving means and the other displacement signal to the horizontal axis moving means in response to the pulses of the pulse train and blocking the displacement signals during the absence of pulses of the pulse train.

Claim 12

A navigational system of the kind described in claim 7 in which the image of the celestial body is realigned with the reference point by moving the telescope and the measuring circuit includes means connected to the telescope for providing pulse trains in which each pulse and each interval between pulses correspond to a predetermined angular movement of the telescope, inverting means connected to the pulse train means, and counting means connected to the pulse train means and to the inverting means for counting the pulses and intervals between pulses to provide signals corresponding to the angular displacement of the telescope.

Claim 13

A navigational system of the kind described in claim 11 in which the pulse train means includes two encoders, one encoder arranged with the telescope to provide a pulse train corresponding to the angular movement of the telescope about its vertical axis and the other encoder arranged with the telescope to provide another pulse train corresponding to the angular movement of the telescope about its horizontal axis; the inverting means inCludes two inverters, each inverter being connected to a different encoder; and the counting means includes an up-down counter connected to the other encoder and to the inverter connected to the other encoder and providing a measurement signal corresponding to its count, a comparator connected to up-down counter, to a ground reference and to the displacement signal means compares a displacement signal corresponding to movement of the telescope about its horizontal axis with the ground reference and provides a signal corresponding thereto to the up-down counter to control the counting of direction of the up-down counter so that the count in the up-down counter corresponds to the zenith angle of the celestial body, a pulse source providing a pulse prior to each realignment of the telescope with the celestial body, and a counter connected to the pulse source, the one encoder and to the inverter connected to the one encoder so that the pulse from the pulse source periodically clear the second mentioned counter resulting in the count in the second mentioned counter corresponding to the change in azimuth angle of the celestial body and providing another measurement signal corresponding to its count.

Claim 16

A method of the kind described in claim 13 in which the computing is done in accordance with the following equation: East Longitude R.A. - G.S.T. + phi ; where lambda is the latitude angle, phi is the hour angle, delta is the angle of declination of the celestial body, d psi /dt is the rate of change of the azimuth angle of the celestial body, d Nu /dt is the rate of change of the zenith angle of the celestial body, omega is the rotational speed of the earth about its polar axis, R.A. is the Right Ascension of the celestial body, and G.S.T. is Greenwich Sidereal Time.