glast large area telescope: a review of the lat egse plan january 24, 2005 mike huffer

GLAST LAT Project

M. Huffer 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

A review of the LAT EGSE Plan

January 24, 2005

Mike [email protected](650) 926-4269

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

GLAST LAT Project

M. Huffer 2

OutlineOutline

• Objective was to define the components necessary to: – support LAT development & test from lab through observatory

• Enumerate constraints:– space/craft (S/C) “implementations”– test-executives

• The VSC (Virtual Space/Craft) …• Enumerate a set of test, development, and integration Environments

– For each environments specify:• logical block diagram (identifies necessary components)• S/C implementation used• test-executives used• S/C to LAT harness differentiation• identify hot issues

• Goals:– preserve continuity of test environments– minimize number of different harness– compile “issues” list and an implementation plan

GLAST LAT Project

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Space-craft implementationsSpace-craft implementations

• The “real thing”• The Spectrum-Astro Instrument Simulator (SIIS)• The SLAC SC simulator (VSC)

GLAST LAT Project

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Test-Executives (T/E)Test-Executives (T/E)

• Generic requirements for a Test-Executive:– monitors the safety and health of its equipment under test– controls the equipment under test– performs necessary real-time analysis of equipment’s telemetry– relays telemetry to science analysis center for off-line analysis

and achieving• LAT’s EGSE model based on the necessity for two different types of

T/Es based on use:– Instrument commissioning– Instrument acceptance and validation

• Instrument validation & operation– Must treat the instrument as if it were operating in its fly-away

context• Instrument commissioning:

– requires precise control of the instrument under test– must be highly responsive– must have “fat” telemetry pipes for rapid turn-around of analysis

GLAST LAT Project

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Test-Executive numbersTest-Executive numbers

• I & T and FSW’s differing emphasis required 2 more Test Executives:

– LTX

• uses the instrument to develop and test its software

– LATTE

• used by the sub-systems to develop the instrument

• used by I & T to test both the instrument and FSW

• If four were not enough, additional requirements required yet more:

– AstroRT

• required for interface validation and observatory operation

– ISOC test-executive (ITE)

• may be driven by MOC choice

• final architecture under development (blend of LATTE5 and ITOS)

GLAST LAT Project

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Test-Executives summarizedTest-Executives summarized

• Test-executives developed for instrument commissioning:– LTX– LATTE4

• Test-executives developed for instrument validation and operation:– LTX++– LATTE5– AstroRT– ITE

• Six are a lot!– even if one makes the case that LATTE is a super-set of LTX they cannot

(should not) be merged:• would lose significant investment in user code base and training

– cannot discard instrument commissioning T/E’s in instrument validation phase:

• valuable and necessary diagnostic tool when things go wrong• schedule dictates may make fat telemetry pipes necessary

• Significant goal of the VSC is to ensure coherency of T/Es used in all environments which require instrument validation and operation:

– common Command and Telemetry Database– common Interface to Space-Craft (independent of its implementation)

GLAST LAT Project

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Environments requiring EGSE supportEnvironments requiring EGSE support

• Software development and test – Location: Dataflow lab – Prime participants:

• FSW • I & T• ISOC• Subsystems

• Instrument integration and test– Location: SLAC clean room– Prime participants:

• I & T • FSW

• S/C-LAT interface validation:– Location: SLAC clean room and Dataflow lab– Prime participants:

• I & T• Spectrum-Astro

– Must test both functional interface and harness• Thermo-Vac (TV) testing:

– Location: NRL– Prime participant:

• I & T• Electro-Magnetic Interference (EMI) testing

– Location: NRL– Prime participant:

• I & T• Observatory integration and test (from the LAT’s perspective)

– Location: Spectrum-Astro and KSC– Prime participant

• I & T• ISOC

– Mating of S/C and LAT

GLAST LAT Project

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VSC “features”VSC “features”

• The VSC is:– both a physical module and an external software interface to it…– a functional interface (does not emulate S/C mechanics or power)

• No ITAR restrictions• Tests all redundancy (Primary, Redundant and cross-strapping)• Acquires and relays all LAT-centric spacecraft telemetry• Public, well defined, Back-End (ground) interface

– allows use by more then one type of test executive• Delivery, maintenance, and extensibility issues under LAT control• Extensive and flexible physics simulation

– attitude and re-pointing model– interface to FES– allows time correlation and coherency between spacecraft,

dataflow system, and simulated event data• Relatively inexpensive• Portable

GLAST LAT Project

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HRS

MINS

SECS

TTM637

AB

TC

LK

1553

AB

TC

LK

1553

SCI SCIDISC

ABCDE

VM

ES

C5

SY

ST

RA

N I/O

HardwareHardware

GPS

Primary Science

6U/9S VME crate

Primary 1553

SBC 2304

discretes and reset

Analogs

GLAST LAT Project

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VSC InterfacesVSC Interfaces

Time-tone

DAQredundant

GASU

VSC control

TCP/IP

LATcommanding

LAT telemetry

LAT science

VSC Proxy Interface

Test Executive

GPS

VSC

LAT

Back-EndFront-End

SIUprimary

Primary

discretes reset

A

1553

A

discretes reset

B

1553

B

Primary

discretes reset

A

1553

A

discretes reset

B

1553

B

SIUredundant

DAQprimary

Redundant

Science 1-PPS GRB

A

Science 1-PPS GRB

B

Primary

Science 1-PPS GRB

A

Science 1-PPS GRB

B

FES

FES

VSC telemetry

Analogs

GLAST LAT Project

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Proxy (T/E) interfaceProxy (T/E) interface

• Queue for either immediate or deferred (timed) execution on VSC:– Commanding stream

• any arbitrary set of telecommands, in any order from C & T DB– Control stream

• ancillary sequence (for an arbitrary number of cycles)• GRB Message• LAT reset request• assert/Deassert discrete(s)• assert/Deassert SSR “device ready”• select:

– GASU DAQ board and its cross-strapping– SIU and its cross-strapping– Discretes and their cross-strapping

• start/Stop FES• set time

• Receive (asynchronously) telemetry from …– LAT (housekeeping and diagnostics)– LAT Science (events and science diagnostics)– VSC telemetry (analog temperatures, voltages, etc…)

GLAST LAT Project

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EGSE following the instrument through most of EGSE following the instrument through most of its phases…its phases…

• LAT Test-Executives hosting environments (not an EGSE issue)• The Virtual Space-craft (VSC)

– simulates the functional role of the S/C from the LAT’s perspective• Power Resource Box

– presents “flight-like” power interface between LAT and S/C– regulates and monitors S/C power presented to LAT

• External Test Box– allows margin testing of both clock and internal power– synchronizes observatory and external clocks– provides external trigger for dataflow system

• External Crate– emulates either an SIU or EPU– allows monitoring of LAT while operating in fly-away context– allows standalone operation of instrument commissioning Test

Executives, which include:• LATTE4• LTX

GLAST LAT Project

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Software development and test environmentSoftware development and test environment

DISC

HRS

MINS

SECS

TTM 637

A

B

TC

LK

1553

A

B

TC

LK

1553

Dataflow Scenario Interconnect DiagramRev. Date JAN 21, 2005

Local network connection

Serial port connection and adapter

28VPS

PowerResource

Box

28VPS

FES

SIURedundant

GPS Antenna

SIUPrimary

GASU

DAQRedundant

DAQPrimary



SCI

SCI

LCB LCB

LAT Shield

External Test Box

A B C D E

VM

ES

C5

S

YS

TR

AN

I/O

VSC

External Crate

External Clock

28VPS

PDU

JL-1

JL-2

JL-232

JL-233

JL-121

JL-234

JL-235

JL-122

JL-39

JL-124

JL-125

JL-138

JL-145

JL-69

JL-119

JL-120

To platform(s) hosting T/E

GLAST LAT Project

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Software development and test environmentSoftware development and test environment

• VSC assumes role of spacecraft• Little logical difference from instrument test & integration

environment – adds support for physics simulation (FES)

• Harness designed for room specific restrictions– built, tested, in use

• External crate is used to operate:– LATTE4 (I & T, subsystem, and electronics, development)– LTX (FSW development)

• VSC is used to operate:– LATTE5 (I & T development)– LTX ++ (FSW and FSW/Test development)– ITE (ISOC development and eventually flight maintenance)

GLAST LAT Project

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Instrument integration and test environmentInstrument integration and test environment

DISC

HRS

MINS

SECS

TTM 637

A

B

TC

LK

1553

A

B

TC

LK

1553

Clean Room ScenarioInterconnect Diagram

Rev. Date JAN 20, 2005



28VPS

PowerResource

Box

28VPS

SIURedundant

GPS Antenna

SIUPrimary

GASU

DAQRedundant

DAQPrimary



SCI

SCI

LCB LCB

LAT Shield

A B C D E

VM

ES

C5

S

YS

TR

AN

I/O

VSC

External Crate

PDU

JL-1

JL-2

JL-232

JL-233

JL-121

JL-234

JL-235

JL-122

JL-124

JL-125

JL-138

JL-145

JL-69

JL-119

JL-120

External Test Box

28VPS

JL-39

GLAST LAT Project

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Instrument integration and test environmentInstrument integration and test environment

• VSC assumes role of spacecraft• Harness designed to be “flight like”

– Issue: this might be in conflict with physical constraints• External crate is used principally as a diagnostic tool

– LATTE 4 (I & T, subsystem, and electronics, diagnostics, perhaps a part of the total CPT)

– LTX (FSW diagnostics)• VSC is used to operate:

– LATTE 5 (I & T CPT)– LTX ++ (FSW and FSW/Test CPT)

GLAST LAT Project

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TV testing environmentTV testing environment

DISC

HRS

MINS

SECS

TTM 637

A

B

TC

LK

1553

A

B

TC

LK

1553

TV Scenario Interconnect DiagramRev. Date JAN 21, 2005



28VPS

PowerResource

Box

28VPS

GPS Antenna



SCI

SCI

LCB LCB

Thermal VacuumChamber

A B C D E

VM

ES

C5

S

YS

TR

AN

I/O

VSC

External Crate

JL-1

JL-2

JL-232

JL-233

JL-121

JL-234

JL-235

JL-122

JL-124

JL-125

JL-138

JL-145

JL-69

JL-119

JL-120

External Test Box

28VPS

JL-39

Flanges

Power Primary

Power Redundant

SIU Primary

DAQ Primary

SIU Redundant

DAQ Redundant

External Connection

GLAST LAT Project

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TV testing environmentTV testing environment

• VSC assumes role of spacecraft• Harness has two components:

– outside the TV chamber and inside the TV chamber– both harness penetrate chamber through 7 flanges– primary and redundant penetrations must be located close to each

other. This implies 5 sets of flanges which could be located anywhere with respect to each other.

– outside harness is re-used for EMI testing– for inside harness attempt re-use of Spectrum-Astro cables

• Issue: what does reuse imply?• External crate is used principally as a diagnostic tool

– LATTE 4 (I & T, subsystem, and electronics, diagnostics, perhaps forms a part of the total CPT)

– LTX (FSW diagnostics)• VSC is used to operate:

– LATTE 5 (I & T CPT)

GLAST LAT Project

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S/C-LAT interface validation environmentS/C-LAT interface validation environment

Interface Confirmation Scenario

Interconnect DiagramRev. Date JAN 21, 2005



SIISPower

SIURedundant

SIUPrimary

GASU

DAQRedundant

DAQPrimary

LCB LCB

LAT Shield SIIS

External Crate

PDU

JL-1

JL-2

JL-232

JL-233

JL-121

JL-234

JL-235

JL-122

JL-124

JL-125

JL-138

JL-145

JL-69

JL-119

JL-120

External Test Box

28VPS

JL-39

GLAST LAT Project

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S/C-LAT interface validation environmentS/C-LAT interface validation environment

• SIIS assumes role of spacecraft• Uses Spectrum-Astro harness

– issue: will this conflict with proposal of re-use from TV?• This test is conducted only when ICD is either validated or

modified. The goal would be once in the: – dataflow lab– clean-room

• External crate is used principally as a diagnostic tool– LATTE 4 (I & T, subsystem, and electronics, diagnostics,

perhaps forms a part of the total CPT)– LTX (FSW diagnostics)

• SIIS is used to operate:– Astro-RT – acceptance test is re-used from ISIS experience

GLAST LAT Project

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EMI testing environmentEMI testing environment

DISC

HRS

MINS

SECS

TTM 637

A

B

TC

LK

1553

A

B

TC

LK

1553

EMI Scenario Interconnect DiagramRev. Date JAN 21, 2005



28VPS

PowerResource

Box

28VPS

GPS Antenna



SCI

SCI

LCB LCB

EMI Chamber

A B C D E

VM

ES

C5

S

YS

TR

AN

I/O

VSC

External Crate

JL-1

JL-2

JL-232

JL-233

JL-121

JL-234

JL-235

JL-122

JL-124

JL-125

JL-138

JL-145

JL-69

JL-119

JL-120

External Test Box

28VPS

JL-39

Power Primary

Power Redundant

SIU Primary

DAQ Primary

SIU Redundant

DAQ Redundant

External Connection

GLAST LAT Project

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EMI testing environmentEMI testing environment

• VSC assumes role of spacecraft

• Harness has two components:

– outside the EMI chamber and inside the EMI chamber

– re-use external cables from TV

– internal harness (power) must be changed to accommodate:

• NIIS

• Isolation transformer

– issue: There seems to be some difference of opinion about whether or not EGSE must be outside chamber

• External crate is used principally as a diagnostic tool

– LATTE 4 (I & T, subsystem, and electronics, diagnostics, perhaps forms a part of the total CPT)

– LTX (FSW diagnostics)

• VSC is used to operate:

– LATTE 5 (I & T CPT)

GLAST LAT Project

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Observatory test and integration environmentObservatory test and integration environment

Spacecraft Integration Scenario

Interconnect DiagramRev. Date JAN 21, 2005



LCB LCB

External Crate

LAT PC

Observatory

SpectrumAstro EGSE

Spacecraft

LAT

JL-69

JL-39 External Test Box

28VPSExternal

Connection



GLAST LAT Project

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Observatory test and integration environmentObservatory test and integration environment

• The “real thing” assumes role of spacecraft• Harness is now irrelevant• External crate is used to operate:

– LATTE4 (I & T, subsystem, and electronics, diagnostics)– LTX (development of FSW)

• Operation of LAT is now through some (as yet unidentified) Spectrum-Astro EGSE– issue: Can we preserve VSC’s proxy interface and our total

code base, if this EGSE has a back-end interface?• issue: If so, ITAR?

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SummarySummary

• Multiple Test Executives are a forgone conclusion

• External crate and test-box are invariants

• VSC stays until observatory test and integration

• SIIS only used for interface validation

• ITAR issues can be either eliminated or substantially reduced:

– but requires VSC…

• Four additional harnesses are envisioned:

– clean-room operation and “Flight-Like” harness validation

– external harness for EMI and TV

– internal harness for TV

– internal harness for EMI

• Potential LAT schedule drivers:

– VSC completion for FSW and FSW/Test

– Harness design and construction for clean-room

– Internal harness decisions for TV (long-lead times on connectors)

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Implementation plan (1)Implementation plan (1)

• Complete detailed VSC design:– review for go-ahead by interested parties:

• FSW and FSW/Test• I & T• ISOC

• Build four (4) VSC’s:– 2 for Dataflow Lab (testbed and hot spare used in corners)– 2 for I & T (operation and one cold spare)– parts currently on hand (or order) to build two

• estimated four week lead-time for additional parts• incremental M/E cost estimated at 40K$

– prototype completion estimated at four weeks after pulling trigger

GLAST LAT Project

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• Compose substantive harness plan:– can we use only one (“flight-like”) harness throughout the

LAT’s time in the clean-room?– what do the internal harness for TV and EMI look like?– what re-use can be achieved with Spectrum-Astro’s

current harness?• how will re-use affect interface validation?• how will re-use affect harness delivery and schedule?

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• Understand limitations and capabilities of Spectrum-Astro’s observatory EGSE– is there a back-end interface?– can we get its specifications?– can we modify specifications to meet our requirements?– what are the ITAR implications?– what are the consequences with respect to VSC control and

telemetry interfaces?

• The answers to these questions will require close interaction and cooperation with both Goddard and S/A

glast large area telescope: a review of the lat egse plan january 24, 2005 mike huffer

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