[FPSPACE] FW: Gravity Probe B Update -- June 7, 2006
ljk4 at msn.com
Fri Jun 9 17:06:06 EDT 2006
>From: Bob Kahn <kahn at relgyro.stanford.edu>
>Reply-To: kahn at relgyro.stanford.edu
>To: gpb-update at lists.Stanford.EDU
>Subject: Gravity Probe B Update -- June 7, 2006
>Date: Fri, 9 Jun 2006 02:50:01 -0700
>GRAVITY PROBE B MISSION UPDATE FOR 7 JUNE 2006
>GP-B DATA ANALYSIS & RESULTS ANNOUNCEMENT STATUS
>Note: The complete status overview of the GP-B data analysis process &
>results announcement from last month's GP-B Mission Update is posted at the
>top of our GP-B Home page: http://einstein.stanford.edu. Following is a
>brief summary of our activities and accomplishments during the past month.
>We are continuing to progress through Phase II of the data analysis
>process, which began at the beginning of March and is scheduled to run
>through late August 2006. During Phase II, our focus is on understanding
>and compensating for certain long-term systematic effects in the data that
>span weeks or months. The primary products of this phase will be monthly
>spin axis orientation estimates for each gyro, as well as refined daily
>spin axis orientation estimates. In this phase, the focus remains on
>individual, rather than correlated gyro performance.
>Over this past month, our telescope team completed a careful analysis of
>data collected from the science telescope over the course of the mission.
>We now have a thorough understanding of the telescope system performance.
>Consequently, some subtle systematic errors introduced into the science
>data by the telescope are now being addressed in the data analysis process.
>Likewise, we are studying the performance of the SQUID gyro readout system,
>the gyro rotor dynamics, and the gyro suspension system.
>Our Stanford GP-B Public Affairs Coordinator has begun working with the
>Public Affairs Office at the NASA Marshall Space Flight Center to plan a
>formal public announcement of the results. We expect to announce the
>results in April 2007.
>GP-B SPACECRAFT & PAYLOAD STATUS AT A GLANCE
>Mission Elapsed Time: 778 days (111.1 weeks/ 25.5 months)
> --IOC Phase: 129 days (4.2 months)
> --Science Phase: 352 days (11.6 months)
> --Final Calibration Phase: 43 days (1.3 months)
> --Extended Science Phase: 4 days
> --Post Mission Phase: 250 days (35.7 weeks/ 8.2 months)
>Current Orbit #: 11,464 as of 3:00 PM PDT
>Spacecraft General Health: Good
>Roll Rate: Normal at 0.04 rpm (25 minutes per revolution)
>Gyro Suspension System (GSS): All four gyros digitally suspended
>Gyro Spin Rates: ~0.52 rpm (spinning at nominal roll rate prior to
>spacecraft roll down)
>Dewar Temperature: ~249.0 K and rising ~0.23 K/day
>Global Positioning System (GPS) lock: Nominal
>Attitude Control System: Magnetic Sensing System (MSS) control
>Pointing Error: (XY/Pitch-Yaw Axes) 2.0 degrees RMS;
>Roll Phase (Z Axis) Error: 5.8 degrees RMS
>Telescope Readout: Pointing performance too low to lock onto guide star
>Command & Data Handling (CDH): B-side (backup) computer in control
>Multi-bit errors (MBE): 1 in CCCA Backup computer; 2 in GSS computers; 0 in
>MISSION DIRECTOR'S SUMMARY
>On Mission Day 778, both the GP-B space vehicle and payload continue to be
>in good health. All active subsystems, including solar arrays/electrical
>power, Experiment Control Unit (ECU), flight computer, star trackers,
>magnetic sensing system (MSS) and magnetic torque rods, gyro suspension
>system (GSS), and telescope detectors, are performing nominally.
>Preparations for placing the spacecraft in a hibernation state will be
>completed in about two weeks.
>The spacecraft is currently in the middle of its 5th full-sun "season."
>During this 15-20 day period, the plane of the spacecraft's orbit is
>orthogonal to the sun, and the sun shines broadside on the spacecraft
>throughout each orbit around the Earth. Thus, as we noted in last month's
>update, this is a good time to view the spacecraft if it passes overhead in
>your neighborhood. The best viewing times are the dawn and twilight hours.
>The temperature inside the Dewar has now warmed to ~249.0 kelvin, and its
>rate of temperature rise has increased slightly to ~0.23 kelvin per day.
>Because the spacecraft has been in full-sun for over a week now, the
>temperature of the dewar's outer shell has warmed to an average temperature
>of ~282.4 kelvin (9.2 degrees centigrade). As the spacecraft moves out of
>its full-sun season next week, it will be eclipsed from sunlight for part
>of each orbit, causing the dewar's outer shell to cool somewhat and
>continue approaching thermal equilibrium with the rising inner temperature.
>Three multi-bit computer memory errors (MBEs) occurred once again during
>the month of May: one in the CCCA (main) computer and one in each gyro
>suspension computer (GSS1 and GSS2). These memory locations have been
>patched via commands sent from our Mission Operations Center (MOC).
>The GP-B spacecraft has performed exceptionally well since its launch on
>April 20, 2004, with no major failures to date. However, the extent of its
>continued post-mission use is still being determined. Our Stanford Mission
>Operations Center (MOC) is still fully functional, and at least through the
>data analysis period, we plan to activate the spacecraft's communication
>system once a week to monitor its status. Regarding longer term,
>post-mission use of the spacecraft, three options are currently under
>1) Spacecraft Hibernation. We are now in the final stages of preparing the
>GP-B spacecraft to enter a very low-maintenance hibernation state,
>described in last month's update. As required by NASA, we are in the
>process of re-configuring the spacecraft's communication system to
>safeguard it from automatically turning itself on and polluting the already
>crowded space communications channels with unexpected and un-monitored
>signals following an on-board computer reboot. Thus, in the hibernation
>state, it will only be possible to communicate with the spacecraft by
>explicitly sending commands from the ground to power on its communications
>system. Ground station communications with the spacecraft have now been
>discontinued, so all further communications will be via the NASA Tracking &
>Data Relay Satellite System (TDRSS).
>The spacecraft can remain in this hibernation state indefinitely. Should
>funding become available for one or more post-mission experiments, we can
>re-activate any on-board systems required. Ultimately, if it is determined
>that there are no further uses for the spacecraft, we will simply stop
>communicating with it.
>2) Stanford Planet-Finding Proposal. Stanford Research Physics Professor,
>John Lipa, one of the GP-B Co-Investigators, has submitted a proposal for
>part-time use of the GP-B spacecraft to identify planets orbiting stars
>outside our local solar system. If this proposal is funded, various systems
>on-board the spacecraft will be re-activated for collecting the necessary
>data, and a small mission operations team will monitor and control the
>spacecraft from the Stanford MOC.
>3) Air Force Academy Space Operations Training. The Space Systems Research
>Center at the U.S. Air Force Academy (USAFA) in Colorado Springs, CO,
>offers a satellite engineering program called FalconSat in which Air Force
>cadets design, build, and learn to operate small satellites. This past
>March, cadets in the program packed the flight operations control room at
>the privately-owned Space Exploration Technologies Corporation (SpaceX), to
>watch the long-awaited launch of their FalconSat-2 satellite, the second in
>a series of satellites from the FalconSat program. Unfortunately, shortly
>after liftoff, there was a problem during the second stage burn, and
>FalconSat-2 was destroyed.
>Can GP-B offer the USAFA cadets an alternative satellite to operate? Former
>GP-B Program Manager, Gaylord Green, thinks so. While GP-B is orders of
>magnitude larger and more complex than FalconSat-2, it has proven to be
>very robust and reliable on-orbit, and it is ready and available for
>alternative uses. To determine the feasibility of using GP-B on a part-time
>basis for research and training purposes, a professor and several cadets
>from the USAFA are spending three weeks here at Stanford, learning about
>the GP-B spacecraft and evaluating the feasibility of the USAFA using it.
>If the USAFA decides to proceed, a communications module will be sent to
>Colorado Springs, enabling cadets to communicate with the spacecraft in
>realtime from the academy. However, we will also retain the ability to
>jointly communicate and control the spacecraft from our Stanford MOC. Thus,
>if Professor Lipa's proposal for extra-solar system planet identification
>is funded, that research--and possibly other research programs--can proceed
>in conjunction with the USAFA program. A decision from the USAFA on their
>use of the GP-B spacecraft is expected at the end of this month.
>GP-B MISSION NEWS--EVERITT LECTURE & GP-B FACILITIES RELOCATION
>Testing Einstein in Space---A Public Lecture by GP-B PI Francis Everitt
>On Thursday evening, May 18, 2006, GP-B Principal Investigator, Francis
>Everitt, gave a 90-minute free public lecture entitled: "Testing Einstein
>in Space: The Gravity Probe B Mission." The lecture was sponsored by the
>Stanford Continuing Studies program, as part its Brainstorms: New Frontiers
>in Science & Technology lecture series. The 500-seat Hewlett Teaching
>Center in the Science & Engineering Quad here on the Stanford campus, where
>Professor Everitt delivered his lecture, was filled beyond its capacity,
>with some people sitting in the aisles.
>Prior to the evening lecture, Stanford's Dean of Research, Arthur
>Bienenstock, hosted a reception in honor of Professor Everitt and the
>Gravity Probe B program. Among the dignitaries present at the reception and
>lecture were Rex Geveden, Associate NASA Administrator, responsible for all
>technical operations at NASA Headquarters and formerly a GP-B Program
>Manager, and Tony Lyons, current NASA GP-B Program Manager at the Marshall
>Space Flight Center in Huntsville, AL.
>Towards the end of the reception, Dean Bienenstock praised the GP-B
>program, and its leader, Francis Everitt, noting that "[GP-B] is unique
>in many ways: It's the single longest-running project in Stanford's history
>[and at NASA], one of the first (if not THE first formal interdisciplinary
>project at Stanford); it has generated more PhDs than any other single
>project in the University's history. It is also one of the most
>scientifically complex projects ever undertaken at the University, with
>some remarkable spin off inventions that are benefiting a wide range of
>other disciplines today." Dean Bienenstock then went on to acknowledge
>NASA's support and funding and the vision of GP-B founders Leonard Schiff,
>Bill Fairbank, and Bob Cannon. Finally, Dean Bienenstock singled out
>Francis Everitt for his devotion, single mindedness of purpose, and staunch
>leadership: "No where in our whole lives have we ever seen another Francis!
>He is truly special in so many ways."
>At the lecture, Dean Bienenstock introduced Professor Everitt, with remarks
>similar to those he made at the reception. Professor Everitt then talked
>for about an hour, telling the complex story of GP-B by weaving together
>seven interfolded themes:
>1) Testing Einstein
>2) The invention of many new technologies
>3) Collaboration between university departments
>4) Highly successful student involvement in a long-running space program
>5) A remarkable range of spin-offs, some of which made possible other NASA
>missions, including IRAS, COBE, WMAP, and the Spitzer telescope
>6) Collaboration between NASA, academia, and industry
>7) The challenge of managing a flight program with a very highly integrated
>payload and spacecraft
>Professor Everitt's lecture was videotaped, and you can view a streaming
>video version of the entire lecture on our GP-B Web site:
>The Walls Came Tumbling Down
>Stanford's master plan for the campus calls for a new 8.2 acre science and
>engineering quad, dubbed SEQ2, to be built around the spot where the
>two-story blockhouse building that has housed GP-B for the past 11 years
>resides. The overall project calls for the construction of an environment
>and energy building, a new School of Engineering center, a replacement for
>the Ginzton Applied Physics building, and a bioengineering/chemical
>engineering building. The new quad is expected to cost between $375 million
>and $420 million. The phased construction process is tentatively scheduled
>to begin in July 2006 with ground breaking on the environment and energy
>building, and officials hope to finish the final building by 2014. Once
>completed, SEQ 2 will give many of the university's science and engineering
>efforts state-of-the-art new facilities in a desirable campus location that
>more cohesively links the western side of campus with the Main Quad and
>As a result of this new construction, our GP-B team spent the last two
>weeks in May moving out of our GP-B building, into offices in three nearby
>buildings, where we will all reside through the end of the GP-B program.
>Our Mission Operations Center has been relocated to a new building, where
>it is now up and running. Also, two computer networks and four major
>computer installations had to be moved, in addition to the staff and our
>40+year archive of documents, photos, drawings, technical papers, and GP-B
>Given that our science team is right in the middle of Phase II of the data
>analysis process, orchestrating such a move was quite a challenge. But, our
>move coordinator and systems administrator rose to this challenge and
>somehow managed to accomplish this move with almost no downtime--and for
>this, they deserve the highest praise.
>On Thursday last week, the area surrounding our old GP-B home was fenced
>off, and this past Monday, the bulldozer arrived--a mechanical
>Tyrannosaurus Rex, right out of Jurassic Park, with Jaws of steel. At 8:30
>AM, the bulldozer began chomping, and by the end of the day, the physical
>home of GP-B--the place where we dreamed, designed, debugged, theorized,
>analyzed, met, talked, ate, slept, monitored and controlled our
>spacecraft--had been reduced to a pile of rubble. Needless to say, it was a
>melancholy day for our GP-B team members. However, we are now up and
>running in our new quarters, and for the most part, life here at GP-B has
>returned to normal.
>You can view a series of photos of the demolition on our GP-B Web site:
>NEXT SCHEDULED GP-B UPDATE IN EARLY JULY, 2006
>Our next regularly scheduled update will be at the beginning of July. Of
>course, we will send out a timely update if there are any important changes
>in the spacecraft's status, or if noteworthy events occur here at GP-B in
>PREVIOUS GP-B UPDATES
>If you wish to read any of our previous updates, our GP-B Web site includes
>a chronological archive of all the updates/highlights (with photos and
>drawings) that we have posted over the past 8 years:
>OTHER LINKS THAT MAY INTEREST YOU
>Our GP-B Web site,
><http://einstein.stanford.edu>http://einstein.stanford.edu contains lots of
>information about the Gravity Probe B experiment, general relativity, and
>the amazing technologies that were developed to carry out this experiment.
>Visual tour of the GP-B spacecraft and payload from our GP-B Web site:
>PDF file containing a 1/20 scale, paper model of the GP-B spacecraft that
>you can download print out, and assemble:
>NASA's Marshall Space Flight Center also has a series of Web pages devoted
>to GP-B: <http://www.gravityprobeb.com>http://www.gravityprobeb.com
>The Harvard-Smithsonian Center for Astrophysics (Cambridge) and York
>University (Toronto), with contributions from the Observatoire de Paris,
>have been studying the motions of the guide star, IM Pegasi for over a
>decade. To find out more, visit:
>In addition, you'll find information in the Guide Star FAQ on our Web site:
>and on pages 18-20 of the Gravity Probe B Launch Companion:
>The Einstein Exhibition at the Skirball Cultural Center in Los Angeles has
>closed.However, you can visit the American Museum of Natural History's
>virtual Einstein exhibit on the Web at:
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>NASA - Stanford - Lockheed Martin
> Gravity Probe B Program
>"Testing Einstein's Universe"
>Public Affairs Coordinator
>Email: kahn at relgyro.stanford.edu
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