An end to GRACE

The successful US/German satellite gravity mission GRACE comes to an end after 15 years

On March 17, 2002, the twin satellites of the NASA/German Gravity Recovery and Climate Experiment (GRACE) were launched in order to make precise measurements of the Earth´s gravity field. GRACE has lasted three times as long as originally planned for more than 15 years. Now it has ended science operations.

Following the age-related failure of a battery cell on one of GRACE’s two satellites, GRACE-2, contact was lost already in September. There are 20 battery cells on each satellite, and GRACE-2 had previously lost seven other cells and was critically low on fuel. Mission managers were able to restore communications with the spacecraft, and analyses revealed the battery had recovered its full voltage. The mission team made plans for one final science collection beginning in mid-October, when the satellites would be in full view of the Sun. Since then, GRACE-2 has periodically hibernated when there was insufficient Sun to power the instruments.

On Oct. 12, as the team prepared to resume science data collection, it became apparent that even with the help of full-Sun conditions, the remaining battery capacity on GRACE-2 would not be sufficient to reliably operate its science instruments and telemetry transmitter. The mission’s Joint Steering Group comprised of all U.S./German mission partners (NASA’s Jet Propulsion Laboratory, Pasadena, California, Deutsches Zentrum für Luft- und Raumfahrt (DLR, the German Aerospace Center) and the Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences) made a decision and announced GRACE-2 will be decommissioned. Since both satellites are required to make the science measurements, the loss of GRACE-2 means GRACE will no longer be able to continue its dual satellite science mission.

“We look back with pride and gratitude on the GRACE mission” says Prof. Dr. Reinhard Hüttl, Scientific Executive Director and Chairman of the Board at the GFZ. “During the 15 years of the mission operation, the satellite tandem has measured the gravity field of the Earth and its variations in a highly precise manner, which helps us, for example, to accurately document changes in groundwater storage or in glacial retreat. Furthermore, the resulting influence on sea level rise can be detected thanks to the GRACE measurements. The mission has, thus, substantially contributed to a better understanding of the system Earth.”

Since 2010, GRACE’s multi-national mission operations and science data analysis teams have overcome numerous technical challenges and developed innovative methods to work around the limitations imposed by aging batteries and limited fuel for flight control to allow the mission to continue to provide its valuable data more than 10 years beyond its intended lifetime.

GRACE-2 is currently orbiting at 305.3 kilometers above Earth, 655 kilometers ahead of and 1,3 kilometers below GRACE-1. With GRACE-2 out of fuel, atmospheric drag on the satellite will increase the separation distance and lower GRACE-2’s altitude relative to GRACE-1. There is no risk of a collision with GRACE-1, and GRACE-2’s orbital altitude does not pose a hazard to other operational satellites.

GRACE-2 will be safely deorbited and is expected to reenter the atmosphere and burn up by mid-to-late November. A few small pieces are expected to survive reentry and reach the ground, but the risk they pose to anyone is minimal and well within NASA requirements for satellite reentry and orbital debris.

Operations of GRACE-1 will continue, with all of its remaining fuel being used to complete a series of accelerometer calibration maneuvers that will be used to improve the scientific return and insights from the 15 year record left by GRACE. All mission activities involving GRACE-1 will be completed by the end of the year, followed by decommissioning of GRACE-1 and atmospheric reentry in early 2018. NASA and the German Space Operations Center will jointly monitor both GRACE satellites as they deorbit and reenter the atmosphere.

“The GRACE Mission Operations Team composed of DLR/GSOC, Airbus Defense and Space GmbH, JPL, University of Texas and GFZ has done a superb job to extend the nominal mission life time by more than a factor of three”, says Prof. Frank Flechtner, co-principal investigator at GFZ. “It is of course a great pity that the monthly observation of mass transport in system Earth has ended after 15 and a half years. However, we now look forward to a successful launch of the successor tandem mission GRACE Follow-on in early 2018. It promises even more precise measurements of the Earth’s gravity field due to an innovative Laser Ranging Interferometer, a technology demonstrator for next generation gravity missions developed by a German/American joint collaboration, and will thus yield further important contributions to Earth system science.”

The principle of the mission: Each of the twin GRACE satellites operates by transmitting microwave signals that are received by the other GRACE satellite. The timing of the received signals is used to precisely measure the small accelerations and decelerations caused by changing mass on the Earth below the spacecraft, which alter the distance between them very slightly. GRACE’s monthly maps of regional variations in global gravity over the past 15-plus years have shown how water, ice and solid Earth material on or near Earth’s surface has moved. To learn more about some of GRACE’s science accomplishments, visit:

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Source: GFZ GEOFORSCHUNGSZENTRUM POTSDAM, HELMHOLTZ CENTRE

http://www.gfz-potsdam.de/en/media-communication/news/details/article/15-jahre-grace/

GRACE is a joint NASA/DLR mission led by the principal investigator Byron Tapley at the University of Texas at Austin and co-principal investigator Frank Flechtner at GFZ. GRACE ground segment operations are currently co-funded by GFZ, DLR and the European Space Agency. JPL manages GRACE for NASA’s Science Mission Directorate in Washington.

For more information on GRACE, visit:

http://www.gfz-potsdam.de/grace

http://www.csr.utexas.edu/grace

http://grace.jpl.nasa.gov

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51 thoughts on “An end to GRACE

  1. Poor old Auntie Grace.

    A confused old biddy, who couldn’t tell molten rock from ice……. but worshiped by some.

    • Quite right, Andy

      It succeeded completely in its mission of generating alarming but nonsensical headlines for 15 years. Worth every cent!

    • worse….couldn’t tell sea level from increased gravity…..positive anomalies in the exact came place for decades

  2. Both the geomagnetic field and the atmosphere of the Earth expand and contract drastically with the small changes in solar activity. Decreasing solar activity for the past decades has allowed most satellites to extend their operating lives by reducing the atmospheric drag and thus fuel consumption. While an engineering and scientific success, it is also a testimony of the failure to predict periodical changes in solar activity.

    As we are in the Eddy solar minimum of the centennial (Feynman) cycle, solar activity should be low one more decade during SC25, and start increasing again afterwards.

    • The names of the centennial lows are Maunder, Dalton, Gleissberg, and Eddy (current).

      Maunder and Gleissberg are also lows of the ~210-year de Vries solar cycle, and Maunder is also a low of the ~1000-year Eddy solar cycle. Increasing millennial activity has made the lows progressively more active. Peak millennial solar activity is expected for the 2050-80 period. Satellites should have a harder time then.

      Notice that I disagree with many solar cycle researchers in that a Maunder-type minimum is not expected for the 21st century. Not even for the 22nd or 23rd. This is because I observe solar cycles in the data for the past 12,700 years, not just the last few centuries.

      • Solar activity reconstructions based on cosmogenic isotopes, 14C and 10Be. There are several of them available and they are in quite good agreement.

        This is an example showing the lows of the 2400-year Bray solar cycle as blue bars.

      • he’s using the wrong one.
        It would be cool if you could click on a graph and see the actual data and method.
        but this is blog science.
        just throw up graphs

      • The first graph has my modifications over a graph initially published by Baolin Tan in his 2011 article: “Multi-timescale solar cycles and the possible implications.” as indicated in the graph as source. I am sure you can find your way in the scientific literature.

      • “…but this is blog science, just throw up graphs.”
        Ha, ha, ha!

        This is from Steve Mosher, the king of drive-by blog science!

  3. Battery s failing, insufficient solar power !!!… But this can’t be true, we’ve been told by our dear leaders that this technology is the way forward

    • “Battery s failing, insufficient solar power !!!”

      Worked well for 15 years, and in a pretty harsh environment. Not too shabby.

      • These batteries are built to tighter specs than the batteries used on earth and as a result are much, much, more expensive.

      • Space isn’t harsh environment for non living things. No air, no water, no dust, no oxidation, no bugs and pest. The only thing to worry about is change in light and temperature, but this isn’t so difficult do cope with, many earthly thing have to do the same

      • Temperature ranges in space are a lot more extreme then you will find here on earth, and the rate of change is faster as well.
        There’s also extra radiation that has to be dealt with.

  4. CAGW sophists used highly inaccurate GRACE data to propagandize their now erroneous assertion that Antarctic Land Ice was decreasing by 130 Billion tons per year for 15 years…

    However, On October 31, 2015, NASA finally came clean and announced that more accurate ICESAT data revealed that from 1992, Antarctic Land Ice was actually increasing by 100 billion tons per year, so NASA’s collective GRACE data error was off by 3.45 TRILLION tons (15years x 230 billion tons/yr)—“Houston, we have a problem…”

    One question NASA never honestly addressed was why it took them 23 years to finally admit Antarctic Land Ice was actually increasing in mass, rather than decreasing… Why, indeed?….

    Obviously, since GRACE data fit the CAGW narrative, NASA decided to use the Politically Correct GRACE data, rather than the Factually Correct ICESAT data..

  5. Despite some misuse of GRACE data by CAGW alarmists, it was an incredibly successful Earth science satellite mission.

    • You say that, but was it really. When you say the data was misused, how do you know that the data was not “just wrong”.
      A lot of assumptions are made when these missions are planned and we all know how wrong some of those have been over the last 25 years.

      • ….and not making adjustments for increased gravity….and showing it as a constant high sea level anomaly

      • NASA had ICESAT data from 1992, and that data inconveniently showed NET Antarctic Land Ice was increasing at around 100 billion tons/year, which completely disconfirmed CAGW’s assured assertion that “unprecedented” melting Antarctic land ice (130 billion tons/yr at an increasing melt rate) would eventually cause 10~20 FEET of Sea Level Rise (SLR) by 2100….

        Too bad the ICESAT data showed CAGW advocates’ rapid SLR increase assertion to be completely impossible…. All the global tide gauge data show SLR has been stuck at around 6~7 inches per CENTURY since 1800, and this century will be about the same, regardless of CO2 levels…

        The CAGW hypothesis is starting to implode…

        If the US Congress was smart (which they clearly are not), they’d submit a FOIA request for all internal NASA e-mails regarding NASA’s decision to use GRACE data over much more accurate ICESAT data, and also determine why it took NASA 23 years to finally announce the ICESAT data…

        This is a huge scandal…

  6. Don’t blame GRACE for results that were predominantly comprised of the applied adjustment.
    As MacIntyre explains here:
    “Understanding the controversy also leads quickly into complicated problems of glacial isostatic adjustments to gravity surveys (GRACE), as the size of these adjustments turns out to be more or less equivalent to the size of the mass loss itself – hardly a desirable property of the method. Over the past decade, the size of generally accepted glacial isostatic adjustments has fallen quite dramatically, with estimates of mass loss falling in conjunction. In retrospect, IPCC AR5 can be seen to have adopted mass loss estimates that were far larger than up-to-date technical literature.”
    https://climateaudit.org/2015/12/02/antarctic-ice-mass-controversies/

    • BAU. Why would they use more accurate and up to date literature, when they could use scarier old cooked up “data” (not data, actually, but, who cares)?

  7. Does this mean Grace gravity measurements will not be misused by fake news specialists for ice thickness claims in Antarctica? I suppose if they were way off before, they won’t need data to continue the flimsy claims.

    • No the CAGW crowd will keep reporting the past data and interpretation. They will even speculate that if GRACE was still flying that it could tell us just how bad things really are. When the data does go their way they are quite willing to expand on older data that did or totally ignore data that counters their position. This is true not only in climate but in other fields I was involved in during my career. And if they do not have total control over the data then they will claim the data is bogus.

    • Radio memories. Our local AM station used to replay those shows in the ’60’s at night. The Green Hornet and The Shadow, too.

  8. So long Grace 1 and 2, you did your job for longer than expected. I look forward to its successor tandem mission GRACE Follow-on in early 2018. It will be much better data and resolution, so will be much harder to ascribe any ‘political’ persuasion to the science. At least in a free and democratic society, the raw data will be ‘honest’. Keep in mind that Grace was only ever measuring the smallest gravity fluctuations from the earths core to surface, and couldn’t tell the difference between a magma distortion below an ice sheet, or a change to the ice sheet itself. We will have to discern what that raw data is with other finely tuned satellites that utilize other technologies such as (InSAR) Interferometric Synthetic Aperture Radar, so that precise distances to sea level or ice cap elevations can be transposed to the Grace data. Which will also show up on longer term imaging from other satellites such as LandSat that map the planet 24/7 in radar images. All this satellite technology will just get more powerful, precise and accurate, like computers have become the last 20 years. This is science at its best and will only get better. I hope we can celebrate this.

  9. However, we now look forward to a successful launch of the successor tandem mission GRACE Follow-on in early 2018.
    In other words: there will be no overlap between missions, so no chance for inter-calibration. All results are free to abuse.

    • Maybe they should ask the Ruskies or China to use one of their spacewalks to replace the batteries so the missions overlap.
      Sarc factor six Mr Chekov! Set a course Mr Sulu.

  10. I think everybody in the CAGW camp are quite happy abot this. Now the extreme snowfall in Greenland last year (and in the last few weeks) will never be measured, and when the next generation GRACE has been launched it will be quite easy to adjust away any unwanted increase in the gap.

  11. The main trouble is that GRACE didn’t measure gravity, it measured microwave lags between 2 satellite. Which, somehow, can translate into gravity measurement by some effect i confess not understanding, but that newtonian law do not allow so it must be relativistic. Some sort of LIGO, but in space

    • It is actually quite simple and in perfect accordance with newtonian law. Over a completly smooth planet without density variations a satellite will move in a perfect ellipse. Over a planet with bumpy topography and/or varying density the satellite orbit will also be slightly “bumpy” due to changes in the gravity field. Where the gravity field is stronger the satellite will be slightly closer to the center of gravity of the planet. If two satellites are in the same orbit they will also come slightly closer to each other since they are in a lower and consequently shorter orbit. It is this change in distance that GRACE measures.

      Note that the often used simplification that the mass of a body is regarded as being concentrated in a point at the center of gravity is an approximation that can only be used at distances that are very large in proportion to the diameter of the body.

  12. so GRACE was a 5 year program, that was said to be very important for knowledge about … yes of course, climate change (as if any else mattered…)… but couldn’t get a replacement for 10 years after the end of planned mission. I guess throwing money through windows, to buy useless fanatics, fans and panels, was more important?

  13. One limitation I have never seen explained, arises from the old equation that g= m1*m2/ d^2. In the GRACE case, the d is not fixed but relates to the distance to a gravity anomaly unravelled by mathematics. This in turn leads to a factor like resolution, where after the math step one can envisage ellipses drawn on the earth surface to show from where the signal mainly arises. What is the size of these ellipses for gravity anomalies that exist, as opposed to theoretical ones? This has always been a key for me, because of a suspicion that many debatable concepts have to be accepted before gravity attribution and magnitude can be stated. In other words, like too many simultaneous equations and not enough variables to solve them. So you have to assume a fix. Or, in more words, how to distinguish two gravity anomalies when one is a small distance below the other. Geoff.

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