Science andOperations
Center forJWST
Science and Operations

Center for JWSTJ Pollizzi, A Krueger, G GreenADASS 2009

Space Telescope Science InstituteS&OC for the JWST Agenda

Brief background of the satellite and mission
 Lessons learned from operating the HST that weplan on applying to JWST Challenges we face in developing the S&OC


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The James Webb Space Telescope
Effective Mirror Size: 6.5m; 18 segments
Sunshield Size: 14.6 m x 21.1 m
Payload Weight: 6500 kg (estimated)
Cold Side Operating Temp: -233C
Hot Side Operating Temp: +85CPlanned Consumables Lifetime: 10 years

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JWST Teams and Responsibilities
Integrated Science Instrument Module (ISIM) – GSFC
•Structure – GSFC/ATK•MIRI- JPL & ESA/European Consortium•NIRSpec- ESA/Astrium•NIRCam – U of Arizona/LMATC•FGS/TFI – CSA/COM DEV

ISIM Radiators- NGST/Ball
Optical Telescope Element (OTE) – NGST/Ball

Backplane Structure – NGST/ATK
ISIM Electronics Compartment (IEC)- GSFC

Deployment Tower - NGST

Sunshield – NGST
Membrane – NGST/SRS
Spacecraft - NGSTMIRI Cryocooler – JPL/NGST
Instrument C&DH - GSFC
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Launch Vehicle & Adapter- ESA/Arianespace
Overall Observatory - NGSTADASS-2009

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JWST Science Instruments

FGS/TF

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JWST Instruments
Instrument

Science Goal

Key Capability

Wide field, deep imaging
NIRCam

0.6 μm - 2.3 μm (SW)Two 2.2’ x 2.2’ SW

Univ. Az

2.4 μm - 5.0 μm (LW)

Two 2.2’ x 2.2’ LW

Multi-object spectroscopy
NIRSpec

0.6 μm - 5.0 μm

ESA

9.7 Sq arcmin Ω
100 selectable targets
R=100, 1000

Mid-infrared imaging
MIRI
ESA/JPL

5 μm - 27 μm

Mid-infrared spectroscopy

4.9 μm - 28.8 μm

1.9’ x1.4’
3.7”x3.7” - 7.1”x7.7”
R=3000 - 2250

Fine Guidance Sensor
FGS/TFICSA

 0.8 μm - 5 μm

Two 2.3’ x 2.3’

Tunable Filter Imager


1.6 μm - 4.9 μm

2.2’ x 2.2’
R=100

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JWST Orbit Transfer

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Key Operations Concepts
JWST Observatory• L2 Orbit - thermal stability, stay light avoidance, stable communications• Orbit Determination & Maintenance• Momentum Management• Event-Driven Operations - efficient and flexible operations•Parallel SI Calibrations - Darks, Sky Flats• Wavefront Sensing & ControlGoldstoneMadridCanberra

Goddard Space Flight Center (GSFC) - Greenbelt• Flight Dynamics Facility (FDF)• Flight Software Maintenance Facility

NASA Integrated Services Network (NISN) - MSFC - Huntsville AL• Ground Network & Voice Communications

JPL Deep Space Network (DSN) - Pasadena CA• Launch Support• Commissioning Support - continuous coverage• Normal Operations Support - 4 hour contact / day

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JPL Deep Space Network (DSN) Ground Stations• CFDP File Transfer Protocol • Downlink rate• Ranging• 458 gbits/day over 2x 4 hour passes• Alternating hemispheres• All science and engineering is recorded for• Clock Correlation
downlink•Engr also downlinked real-time during
pass

Space Telescope Science Institute (STScI) - Baltimore• Science Operations• Proposal Selection, Planning & Scheduling• Event-Driven Operations• Data Archive & Calibration• Mission Operations• Real-Time Operations, Health & Safety Monitoring• Anomaly Resolution, Trending Analysis• Normal Operations 8 x 5• Automated Contacts

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Science and Operations CenterndObservatory
Simulators(OTB/STS)JPL
Deep SpaceNetwork(DSN)

NASA Integrated Services Network (NISN)

S-BaKa-B
andSTScI Science & Operations
Center (S&OC)

GSFC
FlightDynamics
Facility (FDF)

Operations
ScriptSubsystem(OSS)

Project
Reference DB
Subsystem(PRDS)

FlightOperations
Subsystem(FOS)

Wavefront
Sensing &Control Exec
(WFSC Exec)

Data
Management
Subsystem(DMS)

Proposal
Planning
Subsystem(PPS)

Proposals

Data Products

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Proposer9

Lessons Learned from HST

Test as you fly
Use every opportunity and system used during I&T to workout flight operations concepts and approaches(1/3)

Use testing as training events for eventual flight staff

Take best of legacy systems – but not without truecompetitive analysis – and certainly not with any
leftover baggage
E.g. keeping APT, SPIKE and some GSS –but not rest ofplanning Likewise will use MAST, and our Storage Architecture(NSA), but not DADS and likely not OPUS

Use an iterative design approach – but do a goodrequirements analysis upfront

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The requirements gives both a list of what needs to be done
as well as can drive the testing
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Lessons Learned from HST(2/3)

 Have a uniform mechanism for users tointeract with Institute regardless of mission
Using APT as “the” proposal entry tool for both
HST and JWST Using MAST as the “front door” to the archive forall mission data held by STScI Will use GMS as a consistent means for working
with Grant submissions and reporting acrossmissions

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Example JWST APT Input

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Lessons Learned from HST
(3/3)

Maximize efficiency by having onboard event driven
operations
HST uses only absolute timing actions. Looses opportunities
for more exposure time due to incurred overheads (i.e.
waiting a fixed amount of time for a mechanism to move) JWST uses event driven actions – i.e. can proceed with next
step once a mechanism has reported motion completion
 Event concept applies to visits as well. A succeeding visit
can start as soon as its earlier visit successfully completes orfails (within some no-earlier-than constraints)5-Oct-09

i.e. should a guide star acquisition fail, then that visit iscanceled and the succeeding one can start. The scienceprogram can continue even in the wake of failed visits

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Challenges(1/5)

 Funding for Ground Segment components

delayed

Defers startup of key aspects to ground system todifferent times
Impinges on “Test as you fly” since the software is notready when the hardware is And defers integration problems effectively till last major
system comes online (will be years after the first system
is ready)• Will have to rely more on intra-subsystemsimulators/stubs to check out components


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Challenges


(2/5)

Complexity of the Instruments and nature of the data
NIRSpec has a micro shutter array of 798 x 350 shutters (detector
is 2 arrays of 2k x 2k); NIRCAM has 10 sensor arrays, each 2k x 2k
 Data is downlinked as a cube holding successive read-outs as thesensors accumulate charge
 Early indications imply a persistence effect on the detectors
Will require new approaches to doing the calibration pipelines

Environment of the satelliteSolar wind applies a torque to the spacecraft
Momentum management requires an ongoing and active response Factored into both the planning systems and onboard scripting system• Is complicated by the event driven nature of the visits An autonomous system will issue a burn to unload momentum if nototherwise reduced

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NIRSpec Micro Shutter Array

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Challenges(3/5)

 Nature of the data taken

As planned design factored in a 2:1 compressionof science data for recording and downlink
Realized nature of the data did not lend itself to suitable
compression strategies
 Initial response was/is to double the number ofcontacts/day; Was originally 1x 4 hour pass – now 2x
 Now considering compressing a series of delta images(readouts) taken against some initial baseline image.
• Since the delta’s only reflect what’s changed fromread-out to read-out – they are much more suitable
to compression approaches

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Challenges


(4/5)

Dealing with the obsolescence of planned legacy
systems
Original plan from 5 years ago cited the usage of thenexisting systems.
 In the 5 years since the plan – several of the plannedsystems are no longer sustainable for another 5 – 15 yearsfor JWSTHardware-wise JWST is basing its architecture on new
standard configurations
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OPUS, ETCs, use of the Sunfire/Symetrix, MOSS, use ofSybase, STSDAS/IRAF

All servers 64-bit Intel based; most using RHEL5; Databases
using MS SQL ServerADASS-200918

Challenges(5/5)

 Dealing with the obsolescence (continued)
Some systems can be re-implemented using amore sustainable approach

Others require trade studies and evaluations ofnew approaches

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MOSS from Fortran to C++; ETCs and necessary
STSDAS/IRAF routines being redone in Python

i.e. considering LSST’s and NOAO’s pipeline systems asreplacements for OPUSADASS-200919

SummaryUse of Legacy systems is beneficial to a new project, but …
Beware not to freely adopt all aspects of the legacy components


Recognize the lifetime potential of the legacy software/hardwareUse only what works for the new mission
Will it last for the duration of the new mission?

An iterative development approach works well – but don’t ignore
the benefit of having up-front baselined requirements andinterface specifications
You will always find new functions to incorporate though thedevelopment phase – but having a strong base set of requirements
up-front will help assure you don’t miss anything on the way Particularly useful if you need to rephase your development effortsWhenever possible – Test as you fly

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Exercise the system in an operational mode up front (duringnominal testing) then you’ll be less surprised and better trained
when operating for real

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JWST Full Scale ModelSeattle

OrlandoColorado
Springs

Montreal

San Diego
DublinMunichGoddard Space Flight Center
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JWST Links


STScI page http://webbtelescope.org/webb_telescope/NASA page http://www.jwst.nasa.gov/index.html

ESA page http://www.esa.int/esaSC/120370_index_0_m.html

Canadian Space Agency:
http://www.asc-csa.gc.ca/eng/satellites/jwst/default.asp

Northrop Grumman:
http://www.as.northropgrumman.com/products/jwst/index.html

U of Arizona page on NIRCAM:
http://ircamera.as.arizona.edu/nircam/



JPL page on MIRI:
http://www.jpl.nasa.gov/missions/missiondetails.cfm?mission=Webb

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