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News and information relating to the Total Ozone Mapping Spectrometer. To have additional newsworthy items added, please contact Dave Larko. Items in TOMS NEWS SPACE are newer than 12 months. Items dating back farther can be found at the News Archive. Now that the TOMS series of ozone instruments has ended, we are changing our web site to focus on the measurements rather than on the instruments. We are calling the new web site "Measurements of Atmospheric Composition in the UltraViolet - MACUV. At some point, we will shut down the current TOMS web site in favor of this new web site. Comments and suggestions are welcome. This new web site will continue to offer all of the TOMS data, but we are adding the non-ozone data from OMI as well as data from the SBUV/2 instruments. We hope to add data from GOME and GOME 2. Products offered: total ozone, ozone vertical profiles, aerosol (dust, smoke, etc.), reflectivity, cloud fraction, SO2, NO2, BrO, OClO, HCHO, etc. The new Collection 3 OMI data are now available. As mentioned below in the 25-January-2008 news section, the data format has changed. Also, the reflectivity data have now been replaced by radiative cloud fraction data. For details on the new OMI data, see the README PDF document and the Release Details PDF document. New OMI data will be available very soon - probably next week. The data stoppage in December 2007 was due to problems with the spacecraft memory system that have been solved. The Dutch have now provided new instrument data with a revised calibration known as Collection 3. All of the OMI data from launch in 2004 to the present (January 2008) have been re-processed and are being brought onto our web site. The plan is that, next week, we will delete all of the old data and replace it with the new data, including data for all of December 2007 and into January 2008. IMPORTANT NOTE: THE DATA FORMAT HAS CHANGED! There is a problem with the data storage system on the satellite. The OMI data are ok, but the storage system has begun losing some of the spacecraft attitude data. These data are needed to derive the pointing for OMI. They are working on a software fix. But we hear that it could be a couple more weeks until the new software is written and tested. They should then be able to bring the processing of OMI data up to date. correction basis: NOAA-16 SBUV/2 ozone
By mid-2000, the Earth Probe (EP) TOMS instrument degradation became so large that standard correction procedures could no longer produce accurate ozone. The problem is believed to be inhomogeneous degradation of the scanner mirror on TOMS that results in a calibration error that is different at different latitudes. We have warned users that the production EP ozone data should NOT be used for trend analysis. We have now applied a correction to the Earth Probe data that stabilizes the EP ozone record. This empirical correction is based on the NOAA-16 SBUV/2 ozone record, with a solar zenith angle dependence that accounts for much of the spurious latitude dependence observed in the current data. Only the ozone and reflectivity records have been corrected. The aerosol index data and SO2 records are more complex and have not been corrected by this empirical correction. Comparison with the ground network shows that the resulting ozone is stable within ± 1% over the 1996-2005 period. In the period 2002-2005 in the northern hemisphere, there is a residual seasonally-dependent error of ± 1.5% magnitude. These data should still NOT be used as a source for trend analysis since they are no longer independent. The existing Earth Probe ozone and reflectivity data and images were replaced by the corrected Earth Probe ozone and reflectivity data and images on September 4, 2007. The corrected data and images are available on this web site and anonymous ftp site at the same locations as the previous data. For details and complete description of the corrected Earth Probe TOMS ozone and reflectivity data, see the README PDF file. Following the transmitter failure on December 2, 2006, all attempts to revive Earth Probe TOMS failed. Even though the TOMS instrument itself was still working as far as we know, with no way to send data to the ground, there was no point in continuing to operate the spacecraft. After careful review, on May 30, 2007, commands were sent to Earth Probe to deactivate all satellite systems. Subsequent radar scans showed that Earth Probe went from sun-pointing safehold configuration to a slow tumble, confirming that the deactivation commands executed. On December 2, 2006, contact with the Earth Probe spacecraft was lost. Tests confirmed that the transmitter had failed but that the receiver still worked. Presumably TOMS still works, but with no way to bring the data down, there is no point in continuing to operate the spacecraft. The decision has been made to power down the spacecraft late this spring. Since there is no more on-board fuel, it is not possible to do a controlled re-entry. But at its altitude of 730 km., it will be decades before Earth Probe re-enters the atmosphere. EP was designed as a two-year mission. At launch, we guessed that five years was its maximum likely lifetime. Instead, EP returned more than ten years of ozone data. It was a VERY successful mission! The TOMS Science and Data Processing Team was presented the 2006 William T. Pecora Award on Wednesday evening, December 13, 2006 at the American Geophysical Union (AGU) conference in San Francisco, CA. The William T. Pecora Award is presented annually to individuals or groups that make outstanding contributions toward understanding the Earth by means of remote sensing. The award is sponsored jointly by the Department of the Interior (DOI) and the National Aeronautics and Space Administration (NASA). The award was established in 1974 to honor the memory of Dr. William T. Pecora, former Director of the U.S. Geological Survey and Under Secretary, Department of the Interior. Dr. Pecora was a motivating force behind the establishment of a program for civil remote sensing of the Earth from space. His early vision and support helped establish what we know today as the Landsat satellite program. The award consists of a citation and plaque, which are presented to the recipient at an appropriate public forum by the Secretary of the Interior and the NASA Administrator or their representatives. The name of the recipient is also inscribed on permanent plaques, which are displayed by the sponsoring agencies. Earth Probe TOMS in safehold On Saturday, December 2, 2006, contact with Earth Probe was lost. There has been no communication with the spacecraft since. NORAD was able to confirm that the spacecraft was intact and Earth-oriented, which tell us that it is still operational and maintaining attitude. On Wednesday December 6 the spacecraft was commanded to go to SAFE mode, in which it points at the sun, which will maintain power indefinitely. NORAD verified that the spacecraft responded and is now sun-pointing. This indicates that the receiver and processor are working. Earth Probe has been operating on its backup transmitter since 1998 when the primary failed. The operations team tried switching to the zenith antenna in hopes that the problem was the nadir antenna, but still no signal was received. This likely means that the transmitter has failed. At this point the probability of recovering looks poor, but we are still trying. High resolution OMI Level-3e data for aerosol, ozone, and reflectivity are now available for the entire OMI mission beginning with October 1, 2004 through the most recent data. The Level-3e data are on a 0.25o x 0.25o grid (where the regular Level-3 data are on a 1.25o x 1o grid). The Level-3e data files are ascii plain-text in a format similar to that used for the Level-3 data files. In view of the good performance of OMI and the calibration problems with EP TOMS, we have discontinued offering near real time Earth Probe TOMS data beginning January 1, 2006. Within a few days we will offer access to the OMI data via the current web page and tools. Later this spring we will make this an Ozone Mapping web page rather than a TOMS web page, since we are moving to an era that is data centric rather than instrument centric. TOMS Calibration Error: The Version 8 algorithm is now used for all TOMS data. For data beginning in year 2000, the calibration has been stabilized relative to NOAA-16 SBUV/2 in the equatorial zone. Because of continuing changes in the optical properties of the front scan mirror that are not well understood, we are now seeing a latitude dependent error that cannot be corrected by a simple calibration correction. The calibration appears to be stable near the equator. But by 50 degrees latitude, there is now a -2% to -4% error in TOMS, a bit larger in the northern hemisphere than in the southern hemisphere. Because of this error, data since 2002 should NOT be used for trend analysis. Version 8 data and products of the TOMS processing algorithm are now here and available for the Nimbus-7 and Earth Probe instruments. For more information and updates of Version 8 of the TOMS processing algorithm, see the Version 8 update web page. Note that all data and product references below this update (i.e. prior to 23 August 2004) display Version 7 data and products. See the smoke from the eastern Alaska fires as viewed by Earth
Probe TOMS on July 11,
July 12,
July 13,
July 14,
July 15,
July 16,
July 17,
July 18,
July 19,
July 20, and
July 21, 2004. TOMS sees the Saharan dust which caused red snow (i.e. desert dust mixed with snow) to fall over portions of Italy on Saturday, February 21, 2004. Early on November 27, 2003, the Earth Probe spacecraft detected what appeared to be a large error in attitude (pitch) and went into safehold, shutting down the instrument and orienting to conserve power. This appears to be identical to what happened in May of this year. We hope to have TOMS operating in a nominal science mode some time during the week of December 1, 2003. See the smoke from the southern California fires as viewed by Earth Probe TOMS on October 26, October 27, October 28, October 29, and October 30, 2003. See the latest press release from NASA and NOAA regarding the near-record 2003 Southern Hemisphere Ozone Hole area. View an MPEG movie (2 Mbytes) or a QuickTime movie (10 Mbytes) of the 2002 and 2003 ozone holes side-by-side from September 22 through October 6 for each year. The TOMS instrument has been fairly stable for the past year. Comparison with the Brewer instrument at Goddard shows that the current calibration is fairly good - TOMS ozone is about 3% higher than the Brewer. Beginning August 1, 2003, we implemented another correction to remove scan angle dependence, but this time the error was small even before correction. (Warning: we have just replaced the data files for August 1-5, 2003 so you should download the new files if you get data on a daily basis.) In summary, the ozone hole images this year should be more accurate than last year. Our Version 8 product will be ready by about the end of September 2003, but we will delay release to possibly early November 2003 in order to avoid confusion during the ozone hole season. See the smoke from the Canadian fires as viewed by Earth
Probe TOMS on June 19,
June 20,
June 21,
June 22,
June 23,
June 24,
June 25, and
June 26, 2003. Early on May 15 the spacecraft detected what appeared to be a large error in attitude (pitch) and went into safehold - shutting down the instrument and orienting to conserve power. This appears to be identical to what happened last August, so we are now trying to understand the source of the problem before turning the instrument back on. We had thought that it was a Single Event Upset - a high energy particle affecting a memory location - but the events are too similar to be coincidence. We hope to have TOMS operating again early next week. The TOMS-EP FOT has declared a Spacecraft Emergency on 15 May 2003 at 0632 UTC (2:32 AM EDT). A Spacecraft anomaly was detected at a 0413 UTC WPS support. FOT management and the TOMS FOT Lead Engineer were notified of the anomaly. FOT management notified the NASA Mission Director. At 00:24:58 UTC on 15 May 2003 the TOMS-EP spacecraft entered Safe Hold Mode (B-Dot Hold Mode 11). Telemetry indicated that flight software detected an apparent loss of nadir pointing and that spacecraft experienced an instantaneous 81 deg. Pitch error. B-Dot 11 controls the spacecraft using the torque rods and magnetometer to shed excess momentum and maintain the pitch momentum bias vector perpendicular to the orbit plane, rotating at two Revolutions Per Orbit (RPO). The spacecraft and instrument transitioned to safe modes without incident and are power and thermal safe. This anomaly is very similar to one experienced by TOMS-EP on 2 August 2002. On 2 August 2002 both the DP (Data Processor) and SP (Spacecraft Processor), on this occasion the DP was not affected but the SP is showing errors. The 2 August 2002 anomaly was attributed to a Single Event Upset (SEU). After a precautionary shutdown at 1622 UTC November 18, 2002 for the Leonid meteor shower, the high-voltage to the Earth Probe TOMS instrument was successfully turned on at 1919 UTC November 19, 2002. All appears to be running well. Normal data operations resumed on Wednesday, November 20, 2002. Click here for the latest press release from NASA and NOAA regarding the 2002 Southern Hemisphere Ozone Hole. The Earth Probe spacecraft went into safehold last Friday (August 2, 2002) when a single event upset (SEU - basically a high energy particle hitting a memory location) hit the attitude channel. This has happened before, in 1997 and again in 1998. We followed our usual procedure, taking several days to be sure we understood exactly what happened. Then yesterday (August 7, 2002), we put the Earth Probe spacecraft back into normal mode and partially turned the TOMS instrument back on. To be sure that we don't get any more contamination after the cold soak TOMS has been through, we plan to wait until Monday (August 12, 2002) to unstow the mirror and resume taking data. Just being very conservative. We are still having problems with the TOMS calibration, but the instrument now appears to be stabilizing. The good news is that the rapid, wavelength dependent changes have stopped and the instrument appears to be stabilizing at about 25% throughput (which is not a problem - our signal to noise is still very good). Interventions in the calibration were put in on August 1, 2001, and again on December 21, 2001, in order to keep the error within bounds. The errors we have seen so far are only about 5% at worst. The data still cannot be used for trends, but they should be useful for many purposes. While there are no guarantees what the instrument will do in the future, we are cautiously optimistic that we will be able to reprocess and get pretty good accuracy. NASA plans to operate the EP TOMS instrument through 2004 to get overlap with the OMI instrument on Aura. So don't give up on us - we are trying hard! Since August 1 of 2001 we have been applying a correction for the cross track bias in TOMS - an error such that ozone measured looking to the left of the orbital track was consistently lower than ozone measured looking to the right. This error appears to be caused by changes in the optical properties of the front scan mirror. We thought that the instrument was stabilizing, but recent instrument changes are again introducing an error of several dobson units into the TOMS data. TOMS is performing well for purposes that don't require the highest accuracy - ozone hole monitoring, and aerosol detection for example - but current TOMS data should not be used for trend analysis. Data through 1999 are of very high quality; data in 2000 may be used with caution. With the current state of the instrument we can no longer produce high accuracy data on a near real time basis. We must move to a system of delayed processing. Near real time data of limited accuracy will continue to be produced. Then six months to a year later the data will be re-processed with a much better calibration. Users need to be aware of this distinction. We will do our best to continue to provide accurate TOMS data until the launch of the advanced ozone mapper OMI on AURA in early 2004. We have decided to change the EP/TOMS operational processing configuration in order to apply a correction for the cross-track bias errors that have grown large over the past year or so. These data are being made available at the TOMS web site on an operational basis. Data starting August 1, 2001 will be reprocessed with this configuration and made available as well to provide a consistent data set over the 2001 ozone hole season. The data previous to August are the old data, so a discontinuity will be seen at the July 31 / August 1, 2001 boundary. The reprocessed ozone images will also use our new color scale. The cross-track bias correction will remove almost all of the cross-track bias, but will not remove residual long-term changes in ozone due to related instrument degradation. The current EP/TOMS data should not be used for studies of long-term changes in ozone beyond the summer of 2000. In a few months we hope to finalize the calibration and cross track correction for Earth Probe TOMS. At that time we will re-process the entire EP TOMS data set and make it available online as a consistent data set. We regret to announce that the QuikTOMS satellite was lost during launch on Friday (see official press release below). We on the Ozone Processing Team will now concentrate on our efforts to keep Earth Probe operating and in good calibration. Our main problem is that there has been significant instrument degradation, which makes it a challange to meet our goal of 1% long term accuracy. The orbit is stable and the satellite seems to be performing well. The instrument is now over 5 years old, but with a bit of luck we hope to keep it operating for several more years. (Dulles, VA 21 September 2001) - Orbital Sciences Corporation (NYSE: ORB) announced today that the launch of its Taurus rocket, which was carrying the OrbView-4 satellite for ORBIMAGE and the QuikTOMS satellite for NASA, did not achieve the mission's intended orbit. Approximately one and a half minutes after the Taurus rocket lifted off from Vandenberg Air Force Base in California, an in-flight anomaly was observed during the rocket's second stage powered flight. As a result, Orbital believes the rocket released the satellites at a lower altitude and velocity than intended and that they did not achieve a stable orbit. We have done a test reprocessing of the Earth Probe TOMS data implementing a correction for the scan angle dependence. The corrected data look quite good so far, but we are still evaluating the accuracy of the data to see if we need to do one more iteration on the correction term. When we are satisfied with the correction (possibly in September) we will announce that the new data are ready and replace all the online EP data beginning with July 1996. TOMS sees forest fires in Washington State. TOMS data anomalies: in the last year Earth Probe TOMS has begun to experience two problems. 1) a drop in throughput of the instrument of about 50%, and 2) a cross track bias such that ozone measured when looking to the far left of the orbit track is 2 to 3% lower than ozone measured when looking to the far right of the orbit track. This bias is visible in the TOMS images near the equator, where the ozone distribution is most uniform. Both changes appear to result from some real change in the front optics of the instrument, probably the scan mirror, that is not completely understood. The drop in throughput is only a minor problem and is dealt with in the processing. The scan bias is a more difficult problem. We are now (early 2001) beginning to see data dropouts at the far right scan positions. We believe that the TOMS data continue to be usable for most purposes. Average ozone appears to be stable, but individual measurements can have significant error if they are made near the edge of each orbit track. TOMS data past mid 2000 should not be used for trend analysis until the problem is better understood. We plan to carefully characterize the effect on our measured radiances and reprocess the last year or so of data, possibly this summer. Leap year glitch - there was a problem in the software in the ground control center such that the leap year was not being handled correctly. Data for December 31st were being assigned to January 1st. Leap years in the past were handled correctly by this software, so it not clear why it failed this time and it is taking longer to track down the problem than expected. Earth Probe is fine and we have not lost any data. We hope to have everything back on line tomorrow (the 4th). Solar Eclipse. Datum over North America were not processed in the vicinity of the partial solar eclipse. Discovery On-Line EarthAlert annouces a major Saharan Dust Event. Shortly after takeoff from Abidjan, a Kenya Airways Airbus A310 jet carrying 169 passengers and 10 crew crashed in the sea Sunday night. The flight orginiated in Nairobi and was scheduled to stop over in Lagos. Harmattan winds coming down from the Sahara to the north had made skies over Lagos unusually hazy on Sunday and the airport stopped incoming flights. After a three-hour layover, Kenya Airways Flight 431 took off at 9:08 p.m. and crashed into the Atlantic Ocean off the Ivory Coast, one minute later. The noontime TOMS data for 1/30 and 1/31 shows the dust cloud over the KA 431 crash site. The data shows that the dust was quite heavy. Authorites have declined to comment on the whether the plane's engines could have been effected by dust and sand. The NRL Marine Meteorology Division has a thorough analysis of this case on the NRL MMD Aerosol Webpage. Starting COB on Thursday, 30 December 1999, the computers that do the processing for TOMS data to derive ozone will be shut down to comply with NASA's Year 2000 policy. Science processing will resume on Monday, 3 January 2000, at which point all the data collected over the weekend will be processed. The spacecraft and instrument are doing fine. This shutdown will not lead to any loss of data in the TOMS record (unless civilization completely collapses, but then we will have bigger things to worry about than ozone anyway). EP-TOMS has observed the lowest value of ozone ever seen in the Northern Hemisphere since satellites first began ozone measurements in 1978. Again this year, EPTOMS will be shut down on November 17 for approximately 24 hours due to the Leonid meteor shower. It will return to normal operations on November 18. A new TOMS instrument, to be called QuikTOMS, has been approved for launch in August of the year 2000. The current instrument, Earth Probe TOMS, was launched in July of 1996. It was designed as a two year mission but is now entering its fourth year of operation. In order to assure continuity of the ozone data record for the detection of long term ozone trends a new TOMS instrument is needed. The last of the three new TOMS instruments (the Earth Probe and ADEOS instruments have already flown) - Flight Model 5 - is built and in storage. QuikTOMS is being procured under the Goddard RSDO (Rapid Spacecraft Development Office) program, following the procedure under which QuikSCAT was developed and launched. By using a commercial spacecraft and launch vehicle instead of developing a new system, a large savings in cost and rapid development can be achieved. The Orbital Sciences Corporation proposal to build, integrate, and launch QuikTOMS was accepted on July 27, 1999. The spacecraft used will be a MicroStar, which has flown successfully 31 times. The instrument will be launched on an OSC Taurus a four-stage, ground-launched vehicle that can deliver satellites of up to 3,000 pounds into low-Earth orbit. QuikTOMS will share the launch with an Orbcomm satellite. The launch is currently scheduled for August 15, 2000. QuikTOMS will be placed in an 800 km sun synchronous orbit with a 10:30 am equator crossing time. Earth Probe TOMS is now back in full operation. The initial
data appear to be good, but there might be small ozone errors
in the first day of data (January 3) as the instrument warmed
up. We will be watching the instrument for any signs of a calibration
shift as a result of the failover. The Earth Probe spacecraft emergency was terminated at 18:22z on January 2, and TOMS was restored to science mode at 00:20z on January 3, 1999. Recovery was done entirely using magnetic torquing because the on-board fuel supply was exhausted during the failover. The control software has been re-written to do all attitude control using the magnetic torque rods. The orbit is slightly more eccentric than before the failover, but it remains sun synchronous and should be very stable for the next few years. [back-to-the-top] The Earth Probe control team began to de-spin the spacecraft this morning using magnetic torqing. This is a slow process and will take a couple of days. So far everything is going exactly as expected. Next the spacecraft will need to transition to Earth pointing and some software will be uploaded for operation under magnetic control. If everything continues to go well, we could be back in Science Mode next week. Analysis of the Earth Probe failover is continuing. The failover appears to have been caused by an SEU (single event upset) in the clock channel that produced a spurious 81 degree pitch error. The current theory is that one of the attitude thrusters was also bad, which led to continuous firing as the computer tried to spin stabilize the spacecraft in safehold, exhausting the on-board fuel supply. If nothing else is wrong, we should be able to bring Earth Probe back into science mode using magnetic torque control. This will require re-writing the control software. We hope to complete recovery by mid-January. Wish us luck. Earth Probe TOMS went into safehold at 15:11 UT on Sunday, December 13, 1998 and is currently in sun-pointing safe mode. The situation is under study, but it appears that the normal recovery procedure will not be possible and an alternate recovery procedure will have to be used. We expect that TOMS will be out of operation for some time. [back-to-the-top] |
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