Status Report

NASA Gravity Probe B Mission Update 7 June 2006

By SpaceRef Editor

June 14, 2006

Filed under Gravity Probe B, Stanford University, US

NASA Gravity Probe B Mission Update 7 June 2006 — http://images.spaceref.com/news/gravityprobeb.jpg

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 SRE computer

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 consideration:

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 “Š[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: http://einstein.stanford.edu.

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 beyond.

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 memorabilia.

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: http://einstein.stanford.edu.

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 the meantime.

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: http://einstein.stanford.edu/highlights/hlindexmain.html