International Space Station Command and Data Handling

1
International Space Station Command and Data
Handling

• Aleksandrs Kruza

2
Objectives

• Command and Data Handling (CDH) components and
  architecture
• MDM Systems
• Russian Equipment

3
CDH Components

• Multiplexer/Demultiplexers (MDMs)
• Military Standard 1553B bus
• Portable Computer System.

4
MDMs

• Hierarchical Structure
• Crew/Controllers interface to one tier
• Limited by the bus and processing power

5
MDM Hardware
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MDM Hardware

• Mass Storage Device (MSD)
• 300 MB Hard Drive used to store essential data
  while the station is out of contact with the
  ground.
• Also stores back up application software for
  other MDMs

7
MDM Maintenance

• Upon Assembly Complete there will be 44 MDMs on
  station with an expected failure rate of 19.5 per
  year that will require crew maintenance.
• Each MDM as well as its cards and chassis, are
  can be replaced and considered Orbital
  Replacement Units (ORUs)

8
Mil-Std 1553B Bus

• Used to connect MDMs between the tiers and
  locally.
• Connects the Russian Service Module Central
  Computer to the US CC MDM
• A bus controller can connect up to 31 remote
  terminals
• Three data rates of .1, 1 , and 10 Hz

9
PCS

• User level Interface with the CDH allows the crew
  to control core station systems such as GNC and
  EPS.
• Uses a IBM ThinkPad 760XD commercial-off-the-shel
  f (COTS) laptop

10
PCS Software

• Command and Data Software
• Display Software
• 1553 Software
• Command Software
• File and Memory Transfer Software
• Caution and Warning Software
• Time Services
• Status (bus or laptop)

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MDM Systems
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CC MDMs

• Only MDM on tier 1
• Dual fault Tolerant
• Responsible for overall control and monitoring of
  the CDH system

13
INT MDMs

• Tier 2
• Single fault tolerant
• Primary duty is to control ECLSS functions

14
Power Management and Control Unit (PCMU) MDMs

• Controls primary power distribution, PEPS Thermal
  Control System, and the Electrical Power System
• Single fault tolerant

15
GNC MDMs

• Controls navigation, attitude determination, and
  attitude control (non-propulsive)
• Can request the Russian SMTCSW to command the
  Russian Thrusters.
• Unique because both MDMs are always running due
  to the long load times in their software

16
External (EXT) MDM

• Monitors and Controls the various truss elements
  such as the Mobile Transporter, External Active
  Thermal Control System, and the EPS system
• Single fault tolerant

17
Payload (PL) MDMs

• Monitor, controls, and coordinates payloads
  aboard the ISS
• Contains two of the five MSDs on the station and
  the High Rate Data Link

18
Russian Equipment
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Russian Computers

• Different design philosophy
• (???) Service Module Central Computer
• (TBM) Terminal Computers
• Interfaces with the US computers only on a high
  level and share information such as vehicle
  modes, Caution and Warning, and MDM health and
  status
• The GNC MDM and the Service Module TBM exchange
  state vector, mass property, attitude, and
  attitude rate information
• Neither system can actively control the other
  system

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Questions???