Optical telecommunications will be the next technological step in Earth-to-space communication. However, propagation
of an optical beam through the irregular atmosphere results in significant distortion of the signal, necessitating correction
schemes for Earth-to-space communications. Conventional approaches to correct distortions that are based on natural or
artificial guide stars are useful in astronomical imaging, but have practical difficulties or are not adequate to correct the
distortions important for Earth-to-space optical links. Then we proposed a system, which employs an orbiting spacecraft
with a bright laser reference source and a relay mirror, can provide essentially perfect scintillation correction.
For planetary lander missions, the most challenging phase of the spacecraft-to-ground communications is during the
entry, descent, and landing (EDL). Due to the EDL events, the extreme acceleration and jerk cause extreme Doppler
dynamics on the signals received on Earth. In order to support spacecraft-to-earth communications during the EDL
phase, we develop a robust and low complexity carrier frequency estimation and tracking technique that is able to
operate under low SNR and highly non-stationary conditions, common to the adverse EDL scenario. The method
comprises two adaptive filters supervised by a convex combiner. By simulating, it is shown that the investigated convex
combination of individual adaptive predictors is able to outperform the best individual predictor.
NASA has been studying on a new technique called "autonomous radio" for radio receiver since 2004. In an autonomous
radio operation setting, one of the first parameters that we would like to estimate reliably would be the data rate of the
received signal. Knowledge of this parameter is required to carry out maximum-likelihood (ML) detection of other
parameters, such as the carrier phase or modulation type. Although ML estimation of the data rate itself is statistically
optimal, given that there is little knowledge of the incoming signal, this approach is often difficult if not impossible to do
in practice. But if one factor of data rate is mitigated for autonomous radio, the estimation of the data rate can be done
jointly with that of the SNR. NASA has presented two algorithms: SSME and GLRT-Type SSME. The GLRT-Type
SSME outperforms SSME. In this work, we make a modification to GLRT-Type SSME. By simulating, it is shown that
the modified algorithm is able to outperform the SSME and GLRT-Type SSME.
According to the ITU Radio Regulations and CCSDS Recommendation about radio frequency, the 8400-8450 MHz band
is allocated for Space Research Service (SRS) (category B) space-to-earth, and the 8400-8450 MHz deep space band is
critical to the success of deep space missions. Since the 8025-8400MHz Earth Exploration Satellite Service (EESS) band
is allocated for the downlinks of earth exploration satellites, the unwanted adjacent band emission may exceed the
protection criterion established by the ITU-R for the protection of the deep space earth stations by a large amount and
results in harmful interference to the deep space earth station systems. This paper first introduces a conceptual future
scenario with frequency bands. Secondly, the paper discusses the characteristics that are unique to the deep space
downlinks and then presents the characteristics of the EESS out-of-band interference to the deep space downlink X-band.
Finally, the paper describes the effects of the interference on the deep space earth station systems.
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