XTCE: Overview

1
XTCE Overview
XML Telemetry Command Exchange

• Kevin Rice, GST Inc
• Brad Kizzort, Harris Corp.
• 2004

2
Agenda

• Why
• Brief History
• Core Concepts
• Usage Cases
• Quick Example
• Recap
• Questions

3
Why XTCE?

• Leverage commercial marketplace investment in
  acceptance of XML
• Provide for a standard way to exchange telemetry
  information between various parties involved in
  building, testing, launching and managing
  satellite telemetry
• Give the customer (operator) more choices for
  mission ops software instead of being locked into
  a product because of pre-existing database
  formats.
• In other words save money

4
History

• SpaceDTF formed in FY01 at the OMG (Corba, UML,
  etc)
• Published RFP 1 for a standard mission
  operations database format in early 02
• Received three responses, all XML Schemas
• Group decided to combine forces and build one
  Schema for all (TDM Packet)
• OMG Architecture Review board passed the initial
  DRAFT SPECIFICATION in Feb 03
• The SpaceDTF entered into the finalization task
  force (FTF) phase to complete the FINAL
  specification the FTF is still convening

5
History - Whos who

• Key Design Team (Original Submitters)
• European Space Agency
• Science Systems Sam Cooper, Roger Thompson
• ESOC Mario Merri
• US Air force/Mission Operations
• USAF SMC Det 12/VO (Lockheed Martin) Gerry
  Simon (Chair)
• Boeing Communications Satellites
• Janice Champion
• CVS Server Finalization Task Force
• GSFC Mike Rackley
• GST/GSFC Kevin Rice
• Raytheon TSC / UMD / GSFC Ed Shaya (XDF)

6
XTCE Where It Fits in the Schema of Things

• Data Telemetry
• MetaData Formatting (TDM/CCSDS)
• MetaMetaData Description of MetaData Data
  (XTCE)
• It provides for a hierarchical description
  language for mission ops databases
• Telemetry
• Commanding
• Stream information (fixed, variable framing,
  encoding, etc)
• Services, etc
• Algorithms
• Supports Packet (CCSDS) TDM

7
XTCEs hierarchical structure looks like a real
spacecraft
Comm Satellite
EPDS
Battery 1
Repeating components may be defined once
Battery 2
Solar
Propulsion
Subsystem data may be independently developed and
delivered
TTC
8
XTCE Three Core Concepts(everything else in
XTCE is gravy)

• Parameters
• Containers
• Keys ( Containers)

9
XTCE -Telemetry Parameters
Key

• Parameters are
• Immutable pieces of telemetry data (not counting
  bit fields)
• Have a type, such as integer, float, etc
• And a length, bit-order, byte-order and so forth
• Often grouped together with other like data
• - Also called measurands, , etc

A Parameter
10
XTCE - Containers
Container Outer.A

• Containers are
• A convention for describing groupings of
• parameters
• Form a complex data type in telemetry similar to
• C-structs
• May be Sequences of parameters and
• other containers

Parameter
Container Outer
Some Parameters
Container Outer.B
11
XTCE - Keys

• Keys are
• Locations within Containers that
• have identifying information
• -part of the data (APID)
• -have runtime dependent key values

Key
Some Parameters

• Key Definitions have
• a length or width
• an offset
• Key Values
• Specific key values identify a container
• In the telemetry stream

12
XTCE Finding Telemetry Putting Containers
Key Values Together

• In order to actually find data to describe,
• Key Values must be supplied to match against
• the incoming data stream.
• Containers (packets) arrive in any order, usually
• keys key values must be used to match
  telemetry
• so the right container definition can be selected

Key APID10
Some Parameters
13
Example TrivialSat
Telemetry
0
8
16
24
32
ASMfa
MFCtr0
Bat1V
BeaconStatus
Minor Frame 0
MFCtr1
Bat1V
ASMfa
BeaconStatus
Minor Frame 1
Bat1V Battery one voltage, encoded as an 8 bit
unsigned integer, MSB first, calibrated to a
linear 0 to 32 volt curve
BeaconStatus Beacon Status, encoded as an 8 bit
unsigned integer, MSB first where only the first
bit is used, that is treated as a enumerated type
where a 1On and 0Off.
Command
0
8
16
OpCode
Argument(s)
Command Format
On/Off
OpCode170
BeaconPwr
On/OffOn
OpCode170
BeaconPwrOn
14
Example TrivialSat (ParameterSet)
ltParameterSetgt ltFloatParameter
name"Battery1Voltage"gt ltUnitSet/gt ltIntegerDat
aEncoding/gt ltDefaultCalibratorgt ltPolynomialCa
libratorgt ltTerm coefficient"8"
exponent"1"/gt lt/PolynomialCalibratorgt lt/Defa
ultCalibratorgt lt/FloatParametergt ltEnumeratedPara
meter name"BeaconStatus"gt ltUnitSet/gt ltInteger
DataEncoding/gt ltEnumerationListgt ltEnumeration
value"128" label"On"/gt ltEnumeration
value"0" label"Off"/gt lt/EnumerationListgt lt/En
umeratedParametergt ltBinaryParameter
name"minorFrameCtr"gt ltUnitSet/gt lt/BinaryParame
tergt lt/ParameterSetgt
Floating Point Parameter
Is encoded as an integer. Default Integer
Encoding is unsigned 8 bit MS Bit and byte first
Linear calibration
Enumeration Parameter
Encoded as an 8 bit unsigned measurand
8 Bit Binary Parameter
15
Example TrivialSat (ContainerSet)
ltContainerSetgt ltSequenceContainer
name"MinorFrame"gt ltEntryListgt ltParameterRefE
ntry parameterRef"minorFrameCtr"/gt lt/EntryListgt
lt/SequenceContainergt ltSequenceContainer
name"MinorFrame0"gt ltEntryListgt ltParameterRef
Entry parameterRef"Battery1Voltage"/gt ltParamet
erRefEntry parameterRef"BeaconStatus"/gt lt/Entry
Listgt ltBase containerRef"MinorFrame"gt ltRestr
ictionCriteriagt ltComparison
parameterRef"minorFrameCtr" value"0x00"/gt lt/R
estrictionCriteriagt lt/Basegt lt/SequenceContainer
gt ltSequenceContainer name"MinorFrame1"gt . lt/S
equenceContainergt lt/ContainerSetgt
Abstract MinorFrame
MinorFrame0
IS A MinorFrame
Where the minorFrameCtr 0
16
XTCE - Prototyping

• ESA prototyped pre-existing SCOS-2000 mission ops
  database into XTCE and then back again as a proof
  of concept
• Found little loss of information and that the
  translation to XTCE and then back again basically
  worked without issue
• Large increase in database size (order of
  magnitude) BUT
• Not a problem really for modern COTS PCs
• Compressed well
• GSFC started prototyping effort Jan 04
• Show exchange from a database to a variety of
  platforms as part of GMSEC
• ITOS (GSFC)
• ASIST (GSFC)
• Storm/L3
• WIRE first test database

17
XTCE - Recap

• XTCE is an XML Schema and an OMG draft standard
  for describing telemetry and command
  packets/streams
• The FTF will finalize XTCE for full publication
  by OMG.
• XTCE hierarchically describes mission ops
  databases
• Telemetry
• Commanding
• Stream information
• Services
• Algorithms, etc
• Supports Packet (CCSDS) TDM
• Prototyping by ESA complete, GSFC ongoing