Space and astronautical engineering

Satellite Communication (3 CFU): • Satellite communication coverage for Audio/TV Broadcast, Networking, Personal communication: single satellites and constellations in GEO, MEO, LEO orbits with corresponding antenna wide beams beam and high gain beams. Elements of antennas for Space applications; practical antenna systems for the satellite and for the ground segment. Antenna pointing accuracy requirements. Simplified models for signal propagation for satellite communication. • Block diagram of the satellite digital communication transceiver, including channel coding, mapping on the constellation, up-conversion; amplification and propagation; down-conversion, decision, decoding. Link budget, spectral efficiency and Bit Error Rate. Preliminary design of the communication link. • Channel coding: Hamming distance, error detection and correction, Hamming codes, Block codes, Linear Codes, Cyclic Codes (CRC, BCH and R-S), Perfect Codes, LPDC, Convolutional Codes and Viterbi decoding, Concatenated Codes, Turbo-Codes; Error Bursts and interleaving. Elements of probability theory: discrete random variables; Bernoulli distribution; evaluation of BER with Forward Error Correction. • Elements of probability theory: continuous random variables and vectors (probability density function, distribution function, moments); the Central Limit Theorem, the Gaussian probability density function. Thermal noise, Noise Figure and Temperature; evaluation of the Bit Error Rate for the different constellations. • Multiple access techniques: Frequency Division Multiplexing, Time Division Multiplexing, Code Division Multiplexing; Use of the polarization diversity. • Coding and Transmission of satellite/launcher digital telemetry data. • Elements of satellite networking Satellite Radar Sensors (3CFU) • The basic principle of radar: slant range resolution and ground range resolution for radar imaging and radar altimetry. Pulse Repetition Time; Radar range ambiguity and its evaluation for spaceborne radar. • Block diagram of the radar transceiver (Antennas, filters, amplifiers, signal distribution at radio frequency (RF), up- e down-converter devices, A/D e D/A converters, waveform generation and filtering for radar, localization and communication, coding elements); Basic principle Design elements of the sensor and requirements for its different building blocks • Matched filter and pulse compression techniques. The chirp waveform; its generation and its compression; sidelobe control: use for radar imaging and altimetry. • Pulse Repetition Frequency selection for satellite SAR application, Altitude line echo removal; Azimuth ambiguity evaluation. • The synthetic aperture principle, highest stripmap resolution; SAR acquisition modes: StripMap, Spotlight, ScanSAR, TOPS. Antenna requirements for the different modes (size, electronic/mechanical steering capability and accuracy); practical antenna solutions: active phased array vs reflector antennas; foldable antennas, etc... Power budget requirement for SAR in the different acquisition modes. Impact of antenna vibration on SAR image quality and requirements. • Data-rate downlink requirement for the different acquisition modes • radiometric image quality and multilook operation; Noise Equivalent Sigma Zero

There are no specific courses that are required to be passed before this course. The prerequisite for this course is the basic knowledge of Telecommunication Systems for Aerospace or basic elements of signal theory.

• Slides and notes available at the web site https://elearning.uniroma1.it/course/view.php?id=15493 • Satellite Communications, Timothy Pratt, Jeremy Allnutt, JohnWiley & Sons Ltd, Third Edition, 2020 • Principles of Modern Radar, Volume 1: Basic principles, Edited by Mark A. Richards, James A. Scheer, William A. Holm, IET Editor

Despite highly recommended, attendance at the course lectures is not compulsory.

ASSESSMENT TOOLS: The written test (30% of the final grade) lasts 2 hours and it is composed of: - 1 exercise on the preliminary design of a satellite TLC link, including the characteristics of the on-board payload, the ground station and the necessary signal/data coding/processing techniques - 1 exercise on the preliminary design of an Earth observation radar, including the characteristics of the on-board payload, and the required signals/data coding and processing techniques. The written test is positive if at least one out of the two exercises are marked as very good. Test (i) can be replaced with partial preliminary-design tests carried out during the lessons on the Sapienza e-learning platform. The oral exam (70% of the final grade) is composed of three questions on: - characteristics of the Telecommunications payload, of the required processing and coding techniques, and the performance of the individual parts - operation and characteristics of the Earth Observation and/or Tracking Radar; used signal processing techniques; performance of the radar and of its parts. Usually, it is required to reply in oral form to the questions. However, an answer in writing might be required, which is followed by a revision/discussion of the written text. ASSESSMENT METHODS: Assessment of knowledge on the principles of operation of satellite communication payloads and Earth Observation Radar and on the requirements for the platform that hosts them; assessment of knowledge on performance evaluation of satellite radar and communication systems; assessment of the knowledge and ability to make a preliminary design of the scheme of a radio-receiver and radio-receiver for radar and communication applications; assessment of the knowledge and ability to design the required processing and coding techniques. EVALUATION CRITERIA: For each topic (thirty points based rating): sufficient knowledge (rating from 18 to 20); average knowledge (rating from 21 to 23); sufficient skills to apply the knowledge (rating from 24 to 25); good skills to apply the knowledge (rating from 27 to 28); excellent skills to apply the knowledge (rating from 29 to 30 with honors).

The course must be attended in the traditional in-classroom way. Moreover, the video-recorded lectures are progressively made available for the lectures. Therefore, also an asynchronous attendance is possible.