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STEREO and SECCHI Status Consortium 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).
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STEREO and SECCHI StatusConsortium Meeting, Abingdon11-12 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.
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 Nominal distances computed for the November 2001 launch date.
Calibration and PR Opportunity During Phasing Orbits
Telemetry Rates at Various Mission 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
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
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 COR2 COR1 CEB GT EUVI
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 • stereo-all@ares.nrl.navy.mil • stereo-sci@ares.nrl.navy.mil • stereo3d@ares.nrl.navy.mil
Upcoming Meetings • SECCHI PDR NRL 26, 27 September 2001 • Spacecraft PDR APL December 2001 • 3D Workshop Paris 17-20 March 2002