Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2025, V. 22, No. 4, pp. 375-383
Principles of construction of the radar station of the lunar landing module and analysis of the accuracy of measuring the altitude and vertical velocity
D.B. Balter
1 , A.I. Baskakov
2 , V.V. Egorov
1 , A.A. Komarov
2 , M.V. Stalnaya
1 1 Space Research Institute RAS, Moscow, Russia
2 National Research University "Moscow Power Engineering Institute", Moscow, Russia
Accepted: 27.06.2025
DOI: 10.21046/2070-7401-2025-22-4-375-383
The paper examines issues related to the design of onboard radio-technical devices intended to ensure effective control of the lunar landing module at the final stage of landing. It is proposed to use a multi-frequency coherent probing signal of a radar station with the maximum mean square width of the spectrum. The measurement of the altitude and slant range to the lunar surface is carried out using the phase method, and the measurement of the vertical velocity is carried out using the Doppler method. A block diagram of a dual-frequency slant range (height) meter is provided. The smoothing filter at the discriminator output includes an integrator and an RC circuit. Errors of the lunar module landing system, consisting of a multi-beam Doppler velocity vector meter and a range meter to the lunar surface in the direction of each antenna beam, are analyzed. Formulas for errors in measuring altitude, slant range and vertical speed are given. It is indicated that the values of the calculated errors practically along the entire descent path of the landing module satisfy the specified requirements. The errors in measuring the vertical velocity at low altitudes exceed the required values, but they can be reduced by either increasing the time constant of the smoothing filter or by replacing it with a Kalman filter taking into account the model of the module’s descent trajectory.
Keywords: lunar module, coherent probing signal, phase method, Doppler frequency, altitude, slant range, vertical velocity, accuracy, fluctuations, roughness, filtering, measurement errors
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