Excerpts from System Design Document

0823-EX-PL-2014 Text Documents

Georgia Institute of Technology UNP Mission RECONSO

2014-11-20ELS_155973

Telecommunications System Design Document Version D GEORGIA INSTITUTE OF TECHNOLOGY Excerpts from Telecommunications System Design Document Team RECONSO 11/20/2014 10/29/2014

Telecommunications System Design Document Version D TEAM CONTACT Team Member Role Contact Jacqui Green Program Manager jgreen6234@gatech.edu Michael Lucchi Telecom Lead mlucchi@gatech.edu Angel David Telecom Team Member aarciagil@gatech.edu Robert Ainsworth Telecom Team Member rainsworth6@gatech.edu Kreston Barron Telecom Team Member kbarron@gatech.edu Page 1 of 7

Telecommunications System Design Document Version D NOMENCLATURE Astrodev – Astronautical Development, LLC COM – Telecommunications subsystem Eb/N0 – Ratio of received energy-per-bit to noise density FCC – Federal Communications Commission LEO – Low Earth orbit NUG – Nanosat user guide RF – Radio frequency SNR – Signal to noise ratio Tyvak – Tyvak Nano-Satellite Systems, LLC UHF – Ultra high frequency VHF – Very high frequency Page 2 of 7

Telecommunications System Design Document Version D 1. PROJECT OVERVIEW 1.1. INTRODUCTION RECONnaissance of Space Objects (RECONSO) is a student-led cubesat participant in the current University Nanosatellite Program (UNP-8) competition supported by the Air Force Office of Scientific Research (AFOSR). RECONSO will place an optical payload in Low Earth Orbit (LEO) to enable low-cost unqueued space object detection and tracking. Inertial bearing and apparent magnitude measurement will be processed on-board and downlinked to Georgia Tech for further processing and distribution. This data will directly support efforts to mitigate the threat of space debris to national and international space assets by supplementing existing Space Surveillance Network (SSN) sensors. 1.2. SUBSYSTEM INTRODUCTION The primary goal of the telecommunications (COM) subsystem is to downlink the information gathered by the spacecraft and uplink all necessary commands and other information to the spacecraft from the ground station. The link must have a strong enough signal to noise ratio and a high enough data rate to transmit the data recorded by the spacecraft. In its current configuration, the COM subsystem consists of an Astronautical Development, LLC (Astrodev) Beryllium 1 S-Band Transmitter, S-Band Patch Antenna, and S-Band Bi-Directional Amplifier for the downlink and a Tyvak Nano-Satellite Systems, LLC (Tyvak) UHF Radio Flight Unit with a to be determined deployable UHF antenna system for the uplink. This living document will be continuously updated to reflect to reflect the current status of the COM subsystem. Page 3 of 7

Telecommunications System Design Document Version D 1.3. APPLICABLE REQUIREMENTS The telecommunications subsystem requirements are described below in Table 1. This document will be continuously updated throughout the design process to reflect the manner in which these requirements are satisfied. TABLE 1: TELECOM SUBSYSTEM REQUIREMENTS COM Telecommunications Subsystem The telecom subsystem shall provide bi-directional communication between RECONSO and the Georgia Tech Ground Station, or other authorized ground COM-1 stations. MO-4 The telecom subsystem shall downlink object bearings, engineering data, COM-2 telemetry data, and health information to the Georgia Tech Ground Station MO-4 The telecom subsystem shall be capable of downlink speeds of at least 9600 COM-2.1 baud COM-2 The telecom subsystem shall use any extra bandwidth to downlink images COM-2.2 from the visible imager payload to the Georgia Tech Ground Station COM-2 COM-2.3 The telecom subsystem shall maintain a link margin of at least 6dB. COM-2 The telecom subsystem shall receive commands only from the Georgia Tech COM-3 Ground Station MO-4 All communication shall abide by ITU and FCC regulations. The RECONSO team shall obtain the necessary spectrum licenses for operating its space NUG- COM-4 segment radio communication equipment prior to FCR 6.7 1.4. SYSTEM DESIGN The COM system consists of two additional subsystems: the uplink and downlink. In its current form, the uplink consists of a UHF transceiver and a yet to be determined deployable antenna system on the spacecraft and the downlink consists of an S-band transmitter, power amplifier, and patch antenna. Page 4 of 7

Telecommunications System Design Document Version D Transmitters/Transceivers To accomplish the requirements outlined in Table 1, different combinations of transmitters and transceivers have been considered. The current design was motivated by two driving characteristics: 1. The Georgia Tech ground station solely receives on S-band and transmits on UHF frequencies, and 2. An S-band transmitter is necessary to achieve a high enough data rate to transfer large quantities of data, including pictures, from the spacecraft to the Georgia Tech ground station. Moreover, due to commercial availability of transmitters/transceivers, we have specified that the downlink will comprise an S-band transmitter while the uplink will comprise a UHF transceiver operating in a receive-only mode. A patch antenna will be coupled to the S-band transmitter/amplifier in order to maximize the signal strength and data rate between the spacecraft and the ground station. In its current configuration, the aforementioned S-Band transmitter and power amplifier will be coupled to an Astrodev S-Band Patch Antenna. This antenna was selected due to its high gain, low cost, and its ease of integration with the chosen S-Band transmitter. Furthermore, certain aspects of this antenna, including the polarization and mounting substrate, will be customized to meet our mission’s needs. Moreover, this antenna was selected primarily due to its high antenna gain, low cost, and more importantly, its ease of integration with the chosen S-band transmitter. The current iteration of the RECONSO link budgets validates the usability of these selections to meet the COM requirements. Page 5 of 7

Telecommunications System Design Document Version D 1.4.1. TRADE STUDY 1: RADIO FREQUENCY (RF) BAND The first trade study for the COM subsystem analyzes different commercially available RF bands. The most common RF bands for small satellites are S-band and VHF/UHF, both of which have an assortment of available commercial components. Table 4 is a brief comparison of these two RF bands. TABLE 4: RF BAND TRADE STUDY VHF/UHF S-band Frequency Range 0.3-300 2000-4000 (MHz) Low power for antennas and Transmitters have high power Power Required transceivers requirements Link Data Up to 200 kbps Up to 2000 kbps Transmission Rate Modulation schemes Transceiver dependent Transceiver dependent available Lower frequency results in Very small losses due to Losses rain/weather losses weather Components more expensive than VHF/UHF equipment; Transceivers generally less transmitters and receivers are Cost expensive than S-band transmitters usually separate so two components must be purchased Requires mandatory FCC Licensing Depends upon chosen frequency license to test and operate The single most important parameter driving the selection of the RF band was compatibility with the Georgia Tech ground station, which only transmits in UHF and receives in S-Band frequencies. This has the added side effect of resulting in higher available link data transmission rates. As a byproduct of selecting an S-Band frequency, the RECONSO mission will need to acquire an experimental FCC license in order to operate our selected radio equipment Page 6 of 7

Telecommunications System Design Document Version D for both testing and during the actual mission. Page 7 of 7


Document Created: 2014-11-20 17:02:04
Document Modified: 2014-11-20 17:02:04
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