220510 ISDPメモ

ISDP

Mission Elements

Payload

diverse, difficult to teach

  • Driven by Mission Objectives
  • Communications
  • Remote Sensing
  • Navigation
  • Military
  • In-situ Science
  • Resource utilization/Manufacturing
  • Human spaceflight/Space tourism: life-support system

Communications Payloads

Broadcast vs. Duplex:

Broadcast: transmit signals only to end users (e.g. radio)
Duplex: transmit signals in two ways (e.g. network)

Typical Hardware:
  • Antennas
  • Transmitters
  • Receivers
  • Transceivers

Remote Sensing Payloads

Considerations:
  • Passive vs. Active: just observing vs. does something to the target. e.g.) radar
  • Noise, attenuation (loss in signal), scattering (signal bounce off in the atmosphere) etc.
  • Resolution (spatial, temporal, spectral): how many pixel in images

→ spatial resolution: how many pixels per meter
→ temporal resolution: how often you can collect data: changed by the orbit/ the number of satellites (e.g. constellation)
→ spectral resolution: infrared? optical?

  • Access to subject: distance, frequency : affected by velocity and orbit
Typical Hardware
  • Cameras/ Imagers
  • Lidar: radars that use optical light
  • Radiometers
  • Image Spectrometers: e.g.) exo-planets
  • Radar/ SAR

Navigation Payloads

Considerations:
  • Access to subject: (e.g. always see at least 5 GPS satellites)
  • Precision/ Accuracy (e.g. timing functions for ATM)

In-Situ Science

Considerations:
  • in-situ analysis vs. sample return:
    • sample return tends to yield the best data but is much more complex
  • sample/data contamination
    • contamination of bacteria from earth
    • contamination of data (e.g. ice coal sample, melting can change the chemical structure)
Typical Hardware:
  • Mechanical/ robotic systems
  • Sample Cannisters
  • Mass Spectrometers
  • Environmental sensors (pressure, temperature, etc.)
  • Seismometers

Payload Design Process

1. Select Payload Objectives

  • based on mission objectives, constraints, mission concept, etc.

2. Conduct Subject Trades

  • how does the payload interact with the subject?
    • how is it going to do that?
  • what are the performance thresholds?
    • what sort of protection do you need for the sample?
    • what are requirements?
    • what sort of equipment can you use?

3. Develop Payload Operations Concept

  • how does the payload connect the subject to the end user?
    • how do you use the equipment
    • how do you satisfy the need of the end user

4. Determine the required

  • overlap with systems engineering: this is requirements definition

5. Identify Candidate Payloads

  • what are the options for payload instruments and devices?
    • what options do you have that will meet those requirement

6. Estimate Payload Characteristics

  • what are the performance characteristics and interface requirements of the candidates from Step 5?
    • how much power does it need?
    • what it can do
    • how frequently it can capture data
    • what sort of data interface does it use?

7. Evaluate Candidates and Select a Baseline

  • Compare the alternatives & make a preliminary selection

8. Asses Life Cycle Cost & Operability

  • Consider trade-offs between cost and performance
    • does it meet the budget

9. Define Payload-derived Requirements

  • Other mission hardware must directly or indirectly support payload
  • Consider functional interfaces & potential sources of interference
  • This information will drive the design of other subsystems
    • where does it need to be located?

10. Document and Iterate

  • make sure your decisions and supporting information is traceable
  • Don't be afraid to revisit this process.

C&DH

typically simple
Level of Autonomy

  • E1 - Mission execution under ground control, limited onboard capability for safety issues e.g.) mars rover
    • write codes for every moves
  • E2 - Execution of pre-planned , ground-defined, mission operations on-board
  • E3 - Execution of adaptive mission operations on-board
    • spacecraft perform some tasks looking at environment
    • e.g.) Hayabusa guidance system: reached so far with new propulsion system. long time delay to transmit signals to the spacecraft.
  • E4 - Execution of goal-orientated mission operations on-board
    • e.g.) Mars helicopter
    • collect data itself

Mission Data Processing

  • On-board processing - less data transmission (TT&C), more on-board processing (C&DH)

Design Considerations

  • Encoding/Decoding
  • Command Arbitration
  • Input/ Output Channels
  • Data Storage
    • Buffer for mission & operational data
  • Functional Allocation

Components

  • Consider off-the shelf solution!
    • think about the requirements/ the level of autonomy

Mission Operations

  • Mission operations is your mission plan/schedule
    • from launch to disposal
  • Considerations:
    • orbit/trajectory (cruise time, subject availability)
    • attitude (payload, solar panels, TT&C)
    • power (maximum load, duration, recharge rate)

→ what component are used at the same time?
→ discharge capacity is also a problem

    • other environmental factors (heat, EM radiation, etc.)
  • Use quantitative analysis
  • Relate to subsystem requirements
  • Main phases

1. Launch/Deployment
2. (Cruise)
3. Mission Phase (data collection)
4. End of Life

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