Space Telescope Science Institute

The Role of Science and Operationsin the James Web Space Telescope

Mission DevelopmentPresenter D.G. Hunter

Co-authors H.S. Stockman

K.S. Long

Track T5 May 20, 2004

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

JWST Science• Detect First Light (After the

Big Bang) First luminous objects -

protogalaxies, supernovae, black holes

• Assembly of Galaxies Merging of protogalaxies,

effects of black holes, history of star formation

• Birth of Stars and Planetary Systems How stars form in dust clouds How chemical elements are

produced and recirculated

• Planetary Systems and the Origins of Life Formation of planets Direct observation of other

systems Outer Solar System

Observatory Design Features

Science Instruments

Spacecraft Sunshield

25 m2 Primary Mirror

JWST Will Operate at Sun-Earth L2

• L2 allows blocking Sun, Earth & Moon light

• Passive cooling to ~50K

• Stable environment

• Easy communication

Science Instruments

GuiderMIRI

NIRSpec NIRCam

Science InstrumentsMid-Infra-Red Instrument (MIRI)

• 100x sensitivity over previous systems

• Imaging and spectroscopy capability

• 5 to 28 microns• Cooled to 7K by Cryostat or

Cyrocooler• Combined ESA/NASA

contributions

Fine Guidance Sensor (FGS)• Ensures guide star availability with

>95% probability at any point in the sky

• Includes Tunable filters for Narrowband Imaging

• CSA provided

Near Infra-Red Camera (NIRCam)• Detects first light• 0.6 to 5 microns• 4 Imaging modules each with a 2.3’

x 2.3‘ FOV (short 4kx4k, long 2kx2k)

• Coronagraph capability• FPA’s passively cooled to 30K• UofAz/LMATC instrument

Near Infra-Red Spectrometer (NIRSpec)• Studies galaxy formation, clusters,

chemical abundances, star formation, and kinematics

• 0.6 to 5 microns • Simultaneous spectra of >100

objects• 9 square arc minute field of view• FPA’s passively cooled to 30K• Resolving powers of ~100 and

~1000.• ESA provided with NASA Detectors

& Microshutter

Operations• Five year mission lifetime - propellant tanks sized

for 10 years• Guaranteed Time Observations for Instrument

Scientists• General Observing via a peer reviewed proposal

selection process (as for the Hubble Space Telescope)

• Scheduling (long-term and short-term observation plans)

• Event driven execution of uploaded operations plan• On-board procedures, high level commands• Data download and archive• On-the-Fly data calibration

Mission Schedule

Mission ParticipantsNASA

ESA

CSA

Project lead at Goddard Space Flight Center (GSFC)

Observatory Contractor: Northrop Grumman Space Technology (NGST)

Science and Operations Center at the Space Telescope Science Institute (STScI)

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

The STScI Hubble Heritage• Successful preparation and

checkout of 10 instruments (+2 in SM4).

• Proven and evolving software systems for all aspects of science operations: Proposal management Guide star selection (GSC II) Science planning (APT) Scheduling (Spike) Hubble archive “On-the-fly” calibration

management (OPUS) Grants management (GMS)

• Outstanding record of public and astronomical outreach

STScI Role in JWST• Manage the science program from observing program

solicitation and selection to grants management and science outreach support.

• Operate JWST - beginning in commissioning• Develop the science and operations ground systems• Perform ground segment verification• Perform end to end testing• Scientific and Public outreach • Support the Project and JWST teams during the

development phase: Mission architecture & system engineering ISIM & Scientific instruments & ISIM flight software Optics and wavefront sensing and control Science and operations input to many working groups

The JWST Ground System

ProposalPreparation

ProposalSelection

SciencePlanning

OperationsScheduling

FlightOperations

DataManagement

DataArchive

Ground SysEngineering/Maintenance

FlightSystem Eng

Testbeds &Simulators

FlightDynamics

WavefrontControl

InstrumentCalibration

CommandManagement

Flight SWMaintenance

Astronomers

Uplink- Observation Plan- Ephemeris- Commands-Flight S/W-Ranging

JPL Deep SpaceNetwork

JWST Ground Processes and Key Relationships

Downlink- Event Logs-R/T Eng Telemetry-Recorded Telemetry-Ranging-Flight S/W

JWST

- On-Line Documentation- Electronic Forms- Proposal Tools

- TAC review- Electronic Forms

- Long-term plan- Weekly schedule- WFE Sensing- WFE Control- Station Keeping

- Weekly Schedule- Contact Schedule - Eng Activities- Command Loads

- R/T Operations- Uplinks- State evaluation- Data capture- Eng Trend

- L0 Processing- Sci Data QA- SI Calibration- Short Term Storage

- Long-Term Storage(Sci & Eng)- Browsing- Retrieval- SI Calibration- Distribution

- WFE Determination- Mirror Actuator Commands

- FSW Upgrades- Patches- Tables

- SI Procedures- Anomaly Analysis- GSW Requirements- Data Base Management- Vendor OS & Tools- Ground HW / SW Maintenance / Upgrades

- H/W Testbeds- SW Simulators- System I&T- SSM/OTA/ISIMTest Environment

- Orbit Determination- Station Keeping- Ephemeris- Momentum Monitoring

- Anomaly Analysis- Eng Trend Analysis- Degradation Prediction- FSW Requirements

- Algorithms- Reference Data- Performance Reports

- Proposals- Science Data

- Visit Scripts

JWST Ground Processes

The Planning System Interface• Exposure Time calculators

• Optimum background/roll range

• Orientation planning with Guide Star Catalog II Target coordinates in JWST

frame NIRSpec target selection tool Allowable & Optimum roll angles Dither pattern selection and

optimization Predicted glare from bright

objects Acquisition/offset target

selection

• Calibration & engineering operations will also be planned using this planning tool.

Hubble Planning ToolAdvanced Camera for Surveys

Participation in Development• Inform the Observatory development

process of the science and operations drivers for, and consequences of each design decision.

• Ultimate objectives: achieving a high scientific return, reduced lifecycle cost, efficient operations and design.

Influencing Development - 1• Develop and maintain the Mission Operations Concept• Systems Engineering

Participate in requirements development. Evaluate the operations consequences for system level

trades.

• Science Instrument Teams Develop operation concepts with common approaches Develop the calibration plans Gain knowledge of the instruments’ design & behavior Develop the tools and resources the astronomy community

will need for high yield science.

• Flight software Ensure commonality of commanding approaches, syntax and

terminology Develop on-board procedures.

Influencing Development - 2• Integration and Test

Develop and manage the Project Reference Database Provide test conductors who will migrate to the operations

team Develop operations procedures - test against simulators

and with the ground system in the loop with the flight systems.

• Commissioning Develop plans and procedures, working with the flight

systems developers Operate observatory.

Value Added - Mission Simulator• JWST Mission Simulator - simulates execution of science

observations Informed the transformation of the science objectives into the

observatory requirements.

http://www.stsci.edu/jwst/science/jms/index.html Important science influence on requirements

• Field of Regard• Continuous viewing zone• Continuous exposure at same orientation…

Anti-Sun LOS Allowable

ObservatoryField-of-Regard

SUN

Exclusion< 27° fromAnti-Sun Exclusion Zone

< 85° from Sun

Observatory Field-of-Regard (FOR)

Value Added - Fine Guidance Sensor Architecture

• Separation of Fine Guidance Sensor from Near-Infrared Camera. Reduced operational complexity Improved architecture for science Improved management structure.

Value Added - Day in the Life Simulations

• Developed prototype of flight software for event-driven operations including: Executive and processing functions On-board procedure scripts Commands and telemetry for science instruments and spacecraft

• Executed on top of Command and Data Handling System flight code running on a flight representative single board computer.

• Loaded and ran six days of observation plans for three science instruments.

• Produced detailed event logs plus memory and CPU statistics.

• The exercise: developed detailed requirements, confirmed the event driven design with flight like operations, produced flight like prototypes for the flight software.

• Now preparing to implement more complex scenarios.

System Trades - Momentum Management

The JWST attitude required for each science observation results in solar torque being generated by the sunshield.

Unloading momentum disturbs the orbit. Propellant consumption affects the mission lifetime. Constraining the scheduling of observations to manage

momentum accumulation adds significant complexity and may compromise science.

Momentum Profile for First 400 Days of Mission Schedule JMS v1.0_wmk135, 1 Day Max Visit Duration, 40 Nms Limit

0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300 350 400

Start or End of Visit [MJD-56019]

S/C

Mom

entu

m R

SS

[Nm

s]

. 20 65 58 158 43 28Days Between Dumps

Abrupt change in slope due to momentum dump or target change.

Targets at Ecliptic Coordinates (0,*)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

-50 0 50 100 150 200 250 300 350 400

Visit Start Time [MJD - 52000]

Cum

ula

tive

Fra

ctio

nal

Sky

Are

a

Solar Avoidance

10 Day VisitScheduling

0°

30°

45°

60°

15°

90°75°

Ecl

iptic

Lat

itude

Red indicates times where the target is in the field of regard, but a 10 day visit cannot schedule.

Ongoing Challenges• Aspects of operations are highly sensitive to the

flight segment design, such as: Momentum management - smaller sunshield is better Stray light avoidance - larger sunshield is better Both affect scheduling of science observations. Importance of operations involvement in design

trades

• Funding profile - Pressures on Phase A/B funding Lowest lifecycle cost often requires higher initial outlay but

few missions have sufficient early funding. Prioritization of effort in high impact areas.

• Not everyone has learned the same lessons Different missions follow different paradigms Demonstrate merits of approach by example.