1. Payloads AERSP 401A

2. Characteristics of Space Used By Various Missions CharacteristicRelevant MissionsDegree of UtilizationSample Missions Global perspectiveCommunications Navigation Weather Surveillance Some are mature industries; major new advances will come with increased on- board processing IntelSat NAVSTAR/GPS NOAA satellites DSP Ikonos Above the atmosphere Scientific observations at all wavelengths Well developed; space observatories will continue to dramatically change our view of the universe NASA’s Great Observatories Hubble Compton GRT (deorbited) Chandra SIRTF Gravity-free environment Materials processing in space Now in infancy; may be large future applications Industrial Space Facility International Space State Space Shuttle Abundant resources Space industrialization Asteroid exploration Solar power satellites Essentially noneSpace colonies Solar power satellites Exploration of space itself Exploration of Moon and planets, scientific probes, asteroid an comet missions Initial flybys and orbiting has been done; Some landings done or planned; limited manned exploration Manned lunar or Martian bases Apollo Voyager Galileo Cassini

3. Payload Categories and Typical Applications COMMUNICATIONSPECIAL SCIENTIFIC (including Manned) APPLICATIONS Comm. Links Civil comm. Military strategic Military tactical Relay INTELSAT DSCS Irridium Earth looking Remote sensing Earth resources Weather Reconnaissance Early warning Nuclear burst Boost phase tracking Fire detection Oceanography Landsat SPOT DMSP GOES DSP Other Navigation Mfg. In space Solar power relay Search and rescue Space Station S/C repair GPS Spacelab Earth orbiting Planetary Telescopes Space platforms Space station Shuttles Biological Solar Stellar STS/ISS Space Telescopes Pioneer Voyager Galileo Defensive Offensive Space- Based Laser Particle beams SDIO ASATS Mines Other Intelligence ELINT SIGINT Jamming Tethers Burial-in-Space Tugs

4. Roadmap to Payload Design and Sizing Enormously wide range of space payloads Payload design varies dramatically from mission to mission and is critical to mission success –Must have assistance of a payload designer who is expert in the specific payload field from the early stages of the program When done right, payload design is a cooperative venture between the space mission engineer and the payload designer

5. Payload Selection and Design Process StepWhere Discussed 1. Establish Top-Level Objectives1.3 2. Do Subject Trades3.1 3. Select number and type of instruments and broad spectral, energy, or size regime 9.3.2 (Observation), 13.1 (Communication) 4. Define mission operations approach9.3.2 (Observation), 13.1 (Communication) 5. Size the principal instrument(s)9.4.3-5 (Observation), 13.3-4 (Communication) 6. Iterate on steps 2-5 7. Select design features9.4.6 (Observation), 13.3 (Communication) 8. Define support (bus) requirements9.4.7 (Observation), 13.4 (Communication) 9. Ask: Does the system meet mission objectives at the lowest weight, cost, and complexity? Chapter 3 9.2 (Observation), 13.1 (Communication) 10. Iterate on steps 2-8 11. Document

6. Key Issues in Payload Design Process 1.Objectives What are the mission objectives? What characteristics of space are we exploring 2.Subject Trades What is the subject? What different ways are available to observe or interact with? 3.Instrument Number and Type Are multiple instruments appropriate? Will they work well together? 4.Concept of Operations (CONOPS) Coverage mechanism? Tasking and scheduling? Data or material collected? How sent to users? Mission timelines? 5.Instrument Sizing Trade Altitude Aperture Resolution Sensitivity Dwell Swath width Duty cycle FOV size Pointing Coverage 6.Design Features Frequency bands Polarity Optical or antenna design Mechanical configuration Details of subject interaction Details of operations 7.Support Requirements Payload size, weight, and power FOV requirements Pointing, stability, and slewing Duty cycle, data rates Environmental constraints (thermal, sun angle)

7. Payload Performance Sizing High Performance Option –Obtain best available performance –Used in some science and military missions –Examples: HST, Compton, Chandra, Classified Low-Cost Option –Obtain modest performance at low cost –Used for many small satellites and some experiments –Examples: GAS, Piggybacks, Micro/Nanosats Optimized Performance vs. Cost –Obtain highest available performance per dollar –Used in commercial programs, especially communications –Examples: IntelSat, Iridium, Teledesic

8. Subject Trades The subject is what the payload interacts with or looks at. Passive (Uncontrollable) Subjects –Characteristics may be known, but cannot be altered –Includes such things as weather and space environment –Options may exist, even though subject cannot be controlled Controllable Subjects –Characteristics are known and may be altered –Include ground stations, antennas, and receivers The subject is part of the the system trade.

9. FIRESAT Subject Trade What is the subject? –Heat –Fire –Smoke –Atmospheric composition How do we observe it? –IR (heat) –Visible (fire, smoke) –Lidar (atmospheric composition) Selection of the subject and how to observe it are fundamental trades that should be revisited as the design evolves

10. Payload Design Need to be able to: –Make broad first guesses at some of the major parameters –Evaluate instrument types –Develop list of key questions for discussion with payload expert(s) –Estimate critical payload parameters based on assumed parameters –Determine and do system level trades based on key parameters and input from payload expert –Estimate payload size, weight, and power

11. Payload Design Summary Can develop very preliminary estimates of payload parameters Need inputs from individuals knowledgeable in specialized payload design from the time of mission conception –These issues are critical to mission success and there is a real potential for mission the major traces and design constraints However, with a relatively small amount of intelligent guidance, many critical system parameters can be estimated and key system traces can be defined and done. Payload definition and sizing must be a strong mix of payload engineering and mission engineering. Both are critical. The key analysis requirement is to return frequently to the mission objectives and mission utility.