sun earth connection coronal and heliospheric investigation stereo and secchi status consortium...

Sun Earth Connection Coronal and Heliospheric Investigation

STEREO and SECCHI StatusConsortium Meeting, Abingdon

11-12 July 2001

Russ Howard


Outline

• STEREO Mission Status • Spacecraft Status• SECCHI Program Status• SECCHI Technical Status• Upcoming meetings


STEREO Mission Status (1)

• NASA HQ approved the STEREO development plan at a Pre-confirmation Review on 20 May 2001

• This approval turned out to be more difficult than thought, requiring the project to go through a number of program planning exercises

• The primary difficulties were– Insufficient funding in 2000, 2001 and 2002– Increased program reviews due to recent failures

• The funding shortage resulted in Phases A & B being stretched – Phase B goes until March 2002


STEREO Mission Status (2)

• Design Reviews Delayed– SECCHI PDR on 26, 27 September 2001 (from May)

– Spacecraft PDR in December 2001

– CDR about October, November 2002

• A significant problem was that the perceived program risk did not match the funding schedule or the development schedule.

• By delaying launch until November, 2005, these problems were solved


STEREO Spacecraft Names

• Naming contest resulted in very inventive pairs– Comedic: A Dollar Late and A Day Short

– Mythology Figures: Osiris and Isis

– Audio References: AM and FM

• Ahead (A) and Behind (B) were chosen


Spacecraft Status

• Mission design is indicating that there is an interesting lunar eclipse possibility during phasing orbits

• Telemetry rates as a function of mission phase• New configuration is being proposed (approval

within days if not already)• Beacon mode is being planned for, but NASA is

looking for partners to contribute their ground stations to acquire the data.


MISSION DESIGN


STEREO Mission Design

• Place two identical spacecraft in heliocentric orbits: One spacecraft leading the Earth (AHEAD), One spacecraft lagging the Earth (BEHIND).

• Use lunar flybys to impart a mean drift rate relative to the Earth: AHEAD spacecraft +22 degrees/year BEHIND spacecraft –22 degrees/year

• Minimize the eccentricity of the heliocentric orbits in order to minimize variation in apparent diameter of the Sun.

• Launch: November, 2005.


Mission Orbit Extrema

AHEAD BEHIND AHEAD BEHIND

Perhelion 0.879 0.960 0.943 1.003Aphelion 1.040 1.131 0.979 1.083

Worst Case Distances (AU) Nominal Distance (AU)

Nominal distances computed for the November 2001 launch date.


Calibration and PR OpportunityDuring Phasing Orbits


Telemetry Rates at VariousMission Phases


Downlink Data Rates

• Data rates are a function of distance of spacecraft from earth

• 354 to 500 kbps early in mission phase (TBC)• 354.0 kbps - science data rate for 2 year mission• 177.0 kbps - extended mission and S/C checkout• 88.5 kbps - extended mission and S/C checkout• 29.5 kbps - extended mission• 1.2 kbps - extended mission, -V burns and flybys• 11 bps - emergency acquisition mode


Extended Mission Telemetry Rate AHEAD Spacecraft


Extended Mission Telemetry Rate BEHIND Spacecraft


Telemetry Rates Problem

• There may be a problem with the downlink rates.• APL had been working to give us a rate that was

2x the nominal rate. This would have enabled 2x the volume per day early in the mission for the same amount of DSN contact time.

• However the frequency spectrum managers may not be giving the STEREO program sufficient band-width to enable the 2x, nor some of the other telemetry rates in the later phases of the mission.


New Spacecraft Configuration


Spacecraft Configuration Modifications

• Modified center structure to meet ascent phase stiffness requirements

• Shortened observatory height from 66 to 61 inches– Results in increase of max launch mass from 1219 to 1255 kg

• SECCHI electronics box split into two and moved internally

• Baseline concept was over constrained on “SECCHI” panel (-Z) in both volume and mass

• New baseline virtually approved, but location of SWAVES and some of the IMPACT sensors still being worked– NOTE: SWAVES booms are moving in the HI field of view

Sun Earth Connection Coronal and Heliospheric InvestigationNote


SECCHI Status


SECCHI Summary Schedule


SECCHI Program Status (1)

• Schedule– Reflects additional 12 month launch slip (November 2005)

• Peer Reviews– Peer reviews held for SCIP, COR1, COR2, EUVI,

mechanisms, software and electronics

– Peer reviews completed July 9,10 2001 for HI, camera electronics, and focal plane assembly

– System peer review 30 July 2001

– Peer reviews will continue during Phase C


SECCHI Program Status (2)

• Preliminary Design Review– Will be held 26, 27 September 2001 at NRL Building 226

auditorium

– All are welcome, but if you are interested in attending, send us a note so we can make arrangements.


SECCHI Technical Status

• Design is well along• Change in SCIP structure• SEB was split into two boxes

– Computer system (built by NRL/Space Tech Ctr)– Mechanism controller (built by LMSAL)

• Fine Pointing System being added to replace the ISS

• Long lead procurements of CCDs and flight computers under way

• Descope of high speed link to S/C and hardcopy distribution of all STEREO data to all Co-Is


SECCHI SCIP Structure

• APL is proposing to move SCIP to center of spacecraft – decision in next few days.

• We will take advantage of the increased volume to implement a simpler structure for the SCIP– Truss box to a honeycomb optical bench– Interfaces to spacecraft must be agreed to very shortly

– May help the integration of the harness in the new S/C configuration

– Thermal distortion goes in same direction for all telescope tubes

– Access may be slightly improved


New SCIP Concept

GT

EUVI

COR2

COR1

CEB


New SCIP Concept

MEB


SECCHI Electronics Boxes

• SEB (SECCHI Electronics Box)– “Off the shelf” CPU board from NASA/JPL X2000 program

• Received EM CPU Rad750 board from BAE– MIDEX SWIFT program has designs for similar interfaces to

spacecraft and cameras• Negotiating to acquire designs for 1355 and 1553

interfaces from GSFC Flight Electronics Branch – New card for housekeeping

• MEB (Mechanism Electronics Box)– Controllers for all mechanisms except doors– Shares design with Solar-B experiment– Card size same as Solar-B


SECCHI IPS Descope

• EUVI instrument pointing system (IPS) was descoped under the assumption that the S/C pointing would be 1.9 arc sec peak-to-peak

• But APL doesn’t appear to be willing to guarantee that – so requirement is remaining at 3.8 arc sec which would result in an unacceptable science loss

• LMSAL has proposed a simpler, open loop system called the Fine Point System (FPS)– FPS receives pointing error information computed

by software as opposed to a feedback signal generated by hardware in IPS.


Other SECCHI Status

• Procurements of flight hardware in progress– CCD detectors (Delivery Winter/Spring 2002)– RAD750 CPU board (Delivery Summer 2002)

• Tests completed, underway or planned– EUVI Acoustic/vibration– COR1 stray light and objective lens erosion– COR2 lens scattered light– HI stray light– Camera interface– CCD control/noise– Rad750 CPU board– Camera GSE hardware and software


Other SECCHI Descopes

• High speed serial interface to spacecraft was eliminated – SECCHI image data was to be transferred over

this link at a maximum rate of 450 kbps– Now being transferred over the standard 1553

interface at a maximum data rate of 180 kbps – Requires more memory within SECCHI

• Distribution of entire STEREO data set to all Co-Is was descoped– Would like discussion later on concepts that

SECCHI should follow.


SECCHI Communication

• Technical information:– http://projects.nrl.navy.mil/secchi/index.html

• Additional informal site– http://stereo.nrl.navy.mil

• Mail exploders– [email protected]– [email protected]– [email protected]


Upcoming Meetings

• SECCHI PDR NRL 26, 27 September 2001• Spacecraft PDR APL December 2001• 3D Workshop Paris 17-20 March 2002

sun earth connection coronal and heliospheric investigation stereo and secchi status consortium...

Documents

earth connection coronal

various mission phases

russ howard slide

ahead spacecraft

spacecraft pdr

identical spacecraft

stereo development plan

phasing orbits telemetry