ESSE4360 - Payload Design 1.2 Introduction to Space Missions Earth, Moon, Mars, and Beyond Department of Earth and Space Science and Engineering Room 255, Petrie Science and Engineering Building Tel: 416-736 2100 ext. 33854 Email: jjshan@yorku.ca Homepage: http://www.yorku.ca/jjshan
Spacecraft A spacecraft is designed to leave Earth's atmosphere and operate beyond the surface of the Earth in outer space. Spacecraft may either be unmanned or manned vehicles. Spacecraft are designed for a variety of missions which may include communications, earth observation, meteorology, navigation, planetary exploration, scientific research, and so on. The term spacecraft is also used to describe artificial satellites. Introduction to Space Missions 2
Spacecraft Typical Subsystems Attitude control Guidance, navigation, and control (GNC) Communications Command and data handling Power Thermal control Propulsion Structures Payload Ground system Launch vehicle Introduction to Space Missions 3
Subsystem Attitude Control Spacecraft need an attitude control subsystem in order that they may be correctly oriented in space and respond to external torques and forces properly. The attitude control subsystem consists of sensors and actuators, together with controlling algorithms. The attitude control subsystem permits proper pointing for the science objective, sun pointing for power to the solar arrays and earthpointing for communications. Sensors: Inertial guidance system, Orbital Gyrocompassing, Sun sensor, Star tracker, Earth horizon indicator Actuators: Thrusters, Momentum wheels, Precession, Solar sails, Mass distribution or gravity gradient, Spin stabilization, Magnetic field coils or permanent magnets, Pure passive attitude control Introduction to Space Missions 4
Subsystem GNC Guidance refers to the calculation of the commands (usually done by the CDH subsystem) needed to steer the spacecraft where it is desired to be. Navigation means determining a spacecraft's orbital elements or position. Control means adjusting the path of the spacecraft to meet mission requirements. On some missions, GNC and Attitude Control are combined into one subsystem of the spacecraft Navigation methods: GPS, Space Sextant, Landmark Tracking, Earth and Star Sensing, and so on. Introduction to Space Missions 5
Subsystem Communications The communications subsystem, sometimes called the Telemetry, Tracking, and Control (TT&C) subsystem serves as an interface between the spacecraft and the ground system, or between the spacecraft and other spacecraft. The communication subsystem receives telecommands from the ground subsystem, and transmits telemetry from the spacecraft. Introduction to Space Missions 6
Subsystem Command and Data Handling The CDH subsystem receives commands from the communications subsystem, performs validation and decoding of the commands, and distributes the commands the appropriate spacecraft subsystems and components. The CDH also receives housekeeping data and science data from the other spacecraft subsystems and components, and packages the data for storage on a Solid State Recorder or transmission to the ground via the communications subsystem. Other function of the CDH include maintaining the spacecraft clock and state-of-health monitoring (colloquially "watchdog"). Introduction to Space Missions 7
Subsystem Power Spacecraft need an electrical power generation and distribution subsystem for powering the various spacecraft subsystems. For spacecraft near the Sun, solar panels are frequently used to generate electrical power. Spacecraft designed to operate in more distant locations, for example Jupiter, might employ a Radioisotope Thermoelectric Generator (RTG) to generate electrical power. Electrical power is sent through power conditioning equipment before it passes through a power distribution unit over an electrical bus to other spacecraft components. A battery (or batteries) are typically connected to the bus via a battery charge regulator, and the battery is used to provide electrical power during periods when primary power is not available, for example when a Low Earth Orbit (LEO) spacecraft is eclipsed by the Earth. Introduction to Space Missions 8
Subsystem Thermal Control Spacecraft must be engineered to withstand transit through the Earth's atmosphere and the space environment. They must operate in a vacuum with temperatures potentially ranging across hundreds of degrees Celsius. Depending on mission profile, spacecraft may also need to operate on the surface of another planetary body. Introduction to Space Missions 9
Subsystem Propulsion Spacecraft may or may not have a propulsion subsystem, depending upon whether or not the mission profile calls for propulsion. The Swift spacecraft is an example of a spacecraft that does not have a propulsion subsystem. Typically though, LEO spacecraft include a propulsion subsystem for altitude adjustments (called drag make-up maneuvers) and inclination adjustment maneuvers. A propulsion system is also needed for spacecraft that perform momentum management maneuvers. Components of a propulsion subsystem include fuel, tankage, valves, pipes, and thrusters. The TCS interfaces with the propulsion subsystem by monitoring the temperature of those components, and by preheating tanks and thrusters in preparation for a spacecraft maneuver. Introduction to Space Missions 10
Subsystem Structures Spacecraft must be engineered to withstand launch loads imparted by the launch vehicle, and must have a point of attachment for all the other subsystems. Depending upon mission profile, the structural subsystem might need to withstand loads imparted by entry into the atmosphere of another planetary body, and landing on the surface of another planetary body. Introduction to Space Missions 11
Subsystem Payload The payload is dependent upon the mission of the spacecraft, and is typically regarded as the part of the spacecraft "that pays the bills". Typical payloads could include scientific instruments (cameras, telescopes, or particle detectors, etc.), cargo, or a human crew. Introduction to Space Missions 12
Subsystem Ground System The ground system, though not technically part of the spacecraft, is vital to the operation of the spacecraft. Typical components of a ground system in use during normal operations include a mission operations facility where the flight operations team conducts the operations of the spacecraft, a data processing and storage facility, ground stations to radiate signals to and receive signals from the spacecraft, and a voice and data communications network to connect all mission elements. Introduction to Space Missions 13
Subsystem Launch Vehicle The launch vehicle is used propel the spacecraft from the Earth's surface, through the atmosphere, and into an orbit, the exact orbit being dependent upon mission configuration. The launch vehicle may be expendable or reusable. Introduction to Space Missions 14
Space Mission Types Earth Science Communication International Domestic Direct broadcast Miltary Earth observer Weather Navigation Astronomy Military Surveillance Early waring Nuclear detection Intelligence Anti-satellite Planetary & Lunar Exploration Lunar Mercury Venus Mars Jupiter Saturn Uranus Neptune Comet Asteroid Low Earth Orbit (LEO) Medium Earth Orbit (ICO or MEO) Geosynchronous Orbit (GEO) Geostationary Orbit (GSO) High Earth Orbit (HEO) Manned Unmanned Flyby Probe Orbiter Lander Rover Introduction to Space Missions 15
Countries with satellite launch capability First launch by country, from Wikipedia Introduction to Space Missions 16
Some Space Missions Sputnik 1-4 October 1957-1st Earth Orbiter Luna 1-2 January 1959-1st Lunar Flyby Vostok 1-12 April 1961-1st Manned Space Mission Mariner 2-27 August 1962-1st Venus Flyby Mariner 4-28 November 1964-1st Mars Flyby Voskhod 2-18 March 1965-1st Person to walk in space Gemini 6 & 7 - December 15, 1965-1st Space Rendezvous Luna 9-31 January 1966-1st Lunar Lander Zond 5-15 September 1968-1st Lunar Flyby and Return to Earth Apollo 11-16 July 1969-1st Manned Lunar Landing Luna 17/Lunokhod 1-10 November 1970-1st Lunar Rover Mars 3-28 May 1971-1st Mars Lander Salyut 1 - April 19 1971-1st Space Station Pioneer 10-3 March 1972-1st Jupiter Flyby and 1st to leave solar system Anik 1-9 November 1972-1st geostationary communications satellite Columbia - April 12 1981-1st Space Shuttle, destroyed in 2003 Mir - February 19 1986 - Space Station with longest in-orbit operation Galileo - 18 October 1989-1st Asteroid Flyby Hubble Space Telescope - April 24 1990 - Most Important Telescope Mars Pathfinder - 4 December 1996 - Mars Lander and 1st Mars Rover Introduction to Space Missions 17
Canadian Role in Space Technology Many Canadian successes in payload design Canadarm, Canadarm2, Radarsat 1 and 2, MOST. In fact, governmental investment in space industry largely focused on payload systems since early 1970 s. Most commercial activity also focused on payload and information services. ü ü ü ü ü Alouette Anik RADARSAT Canadarm Canadarm2 Introduction to Space Missions 18