Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-40801) (for August 1999) OVERVIEW The YOHKOH Mission is a program of the Japanese Institute of Space and Astronautical Science (ISAS) with collaboration by the U. S. National Aeronautics and Space Administration and the U. K. Science and Engineering Research Council. The YOHKOH satellite was launched on 30 August 1991 from Kagoshima Space Center (KSC) in Japan. The purpose of this mission is to study high energy phenomena in solar flares and the Sun's corona. Under an international cooperative agreement, Lockheed Martin, under NASA contract, is providing a scientific investigation using the Soft X-ray Telescope (SXT), one of the primary experiments of the mission. The SXT was developed at the Lockheed Martin Solar and Astrophysics Laboratory in cooperation with the National Astronomical Observatory of Japan, and the Institute for Astronomy of the University of Tokyo. MAJOR PROGRAMMATIC ACTIVITIES IN THE MONTH All of the programmatic and financial aspects of the program are continuing in a nominal manner. We are still anticipating the RFP for the continuation of operations and data analysis fot FY2000 and beyond in the next month. SOLAR ACTIVITY Success at last - the Sun finally came through with an X-class flare, just at the beginning of this reporting period. It was the first in 1999. Following this the activity subsided rather completely, so that the eclipse of August 11 occurred during a rather quiet corona. SXT experienced no technical difficulties and we had minimal coordinated observing activity. During the first seven months of the year there had been many M flares, so many in fact that the standard flare/microflare distribution function would have predicted 13-26 X-class events (power-law index range 1.8-1.5). The X-class flare was the product of an active region with a bright X-ray sigmoid structure, rather than a delta spot configuration. It was a 1B optical flare, with 1300 SFU at 15,400 GHz and had a type II burst, but no type IV burst. Interestingly, it came from NOAA 8647, not NOAA 8651 which had a colossal sunspot area of 1,370 millionths at about the same time. In mid-August the level of solar activity plummeted, as though the Sun were exhausted following the previous week's X-class flare. The major event was the eclipse, which Yohkoh observed with almost full success. At the end of August, the level of solar activity rose yet again, providing another (the year's second) X-class flare plus five M-class flares. The X-class flare followed a prediction by Big Bear regarding region 8674. Page 2 CAMPAIGNS The eclipse of August 11 was the subject of much coordination, including a "quasi-real-time" display on the Internet on behalf of the 10:00 pm Tokyo news program "Night Station." We provided them with a movie of quarter resolution full disk images. All of the software, both on-board and ground-based, worked fine, and Shimojo_san at ISAS arranged the actual data presentation. A good experience, given our frequent troubles in the past with getting eclipse data to work as predicted! One shortcoming of this eclipse was rather poor PFI coverage. We are distinctly interested in the use of high resolution PFI data to assess the SXT point-response function. Luckily there is archive eclipse data for this purpose, and we can hope for a brighter corona on the next opportunity. Max Millennium Observing Campaign 002, Flares Associated with Sigmoids During Whole Sun Month 3, ran August 18-27. During this campaign, observations of a single sigmoidal active region, AR 8668, were obtained over most of its disk transit. Eruptive events appear to have taken place primarily prior to the start of the campaign. However, one CME was reported by UVCS & LASCO on the 26th, which was associated with a nice limb arcade and cusp in the Yohkoh SXT images. SCIENCE Acknowledging that TRACE EUV images are, at first glance, quite different from SXT images, an obvious question is whether TRACE cool loops have anything to do with SXT hot loops. More specifically, can SXT loops be visible in TRACE images before they heat up to or after they cool down from the temperatures SXT is sensitive to? Nitta looked at many TRACE images that contained the periods during which SXT non-transient loops were seen. The negative result suggests that the SXT loops do not start from cool loops and that they change appearance (e.g., shrink) as they cool down. This is consistent with a more involved study by Nagata, who analyzed EIT data. The Sun finally came through with an "X-class flare" on August 2, the first this year. There had been 1, 3, and 10 such flares in 1996, 1997, and 1998 respectively, as the solar cycle built up towards its maximum. So, by any scheme of extrapolation, we would have expected more than one X-flare by now in 1999. These numbers may be a bit inaccurate, but any way you cut it one would have expected more than one X-class flare in the first seven months of 1999. So how do we explain this astonishing shortfall? The distribution of flare energies, i.e. how many flares per unit peak energy, falls as a negative power law. Thus fewer large flares happen than small ones. But this negative power law has an index in the range 1.5-1.8, and it extends down from the flare range into the microflare and nanoflare. Because it is so flat, the total energy devoted by the Sun to flares is "open-ended" - the single largest flare dominates the total flare energy. Thus, Lingenfelter and Hudson noted some time ago that there really needed to be an upper cutoff in the power-law distribution. In other words, the flare energy distribution would steepen above some threshold energy. Normally this threshold energy can Page 3 be quite high - flares of magnitude X30 are not unknown. But during early 1999, for reasons known to the Sun but not to us, this threshold clearly had dropped by a large factor. So, the 1999 August 2 flare was interesting as an exception testing some sort of rule! The "astonishing shortfall" alluded to above can also be seen in the ratio of numbers of M and X flares Year M's X's 1996 3 1 1997 21 3 1998 94 10 1999 (through July) 83 Zero! The "zero" entry corresponds to an expectation of 13-26 X flares, depending upon the power-law index of the distribution. These "a posteriori" statistics are pretty convincing for the case that the cutoff flare energy was lower - by a factor of 100 or so - than it is normally. PUBLIC USE OF SXT IMAGES We are continuing to make Yohkoh/SXT images available for a variety of uses. Efforts continue to make selected images available on the LMSAL SXT WWW homepage (http://www.lmsal.com/SXT/). We receive requests for the Yohkoh posters (#2 and #3) by way of the form on the SXT homepage. Currently we receive requests via our homepage at the rate of 2 or 3 per day. The WEB access statistics in August were 133905 accesses and 6918 Mbytes transferred. YOHKOH OPERATIONS AND HEALTH Yohkoh and the SXT continue to function very well. SXT experienced a normal level of Single Event Upset (SEU) events during the month: SXT FIL ST Error 02-Aug-99 Pass 3: 990802-1240 Recovered in Pass 4 SXT WRM Error 30-Aug-99 Pass 1: 990830-0309 Recovered in Pass 4 Page 4 DATA FLOW Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Jun-97 469874 190493 1909716 394585 2304301 905466 28.03 Jul-97 8614 1385 32503 431 32934 6559 16.61 Aug-97 7316 987 23136 3519 26655 4990 15.77 Sep-97 7051 1479 33646 9596 43242 8887 17.05 Oct-97 7023 1134 26813 1827 28640 6043 17.42 Nov-97 6691 1376 26297 15306 41603 7131 14.63 Dec-97 6806 1013 28472 2136 30608 5263 14.67 Jan-98 5715 1803 23479 3232 26711 9918 27.08 Feb-98 6606 1644 25257 3606 28863 8989 23.75 Mar-98 6043 2056 23029 10399 33428 10939 24.66 Apr-98 6537 1103 22656 8087 30743 6339 17.09 May-98 7569 1838 28292 19018 47310 9868 17.26 Jun-98 6463 1638 24990 5618 30608 9051 22.82 Jul-98 6810 1892 27046 7357 34403 9970 22.47 Aug-98 5823 1960 22978 14126 37104 11167 23.13 Sep-98 6776 1432 21814 11626 33440 7753 18.82 Oct-98 6573 1901 23520 5198 28718 9220 24.30 Nov-98 6442 1695 25124 26948 52072 9920 16.00 Dec-98 5962 2005 21490 15770 37260 10561 22.08 Jan-99 5494 1825 20087 17620 37707 9622 20.33 Feb-99 5729 1525 30802 9798 40600 10630 20.75 Mar-99 6807 1844 24721 12354 37075 10064 21.35 Apr-99 6715 1371 25113 4179 29292 7791 21.01 May-99 3330 1053 24258 8006 32264 9995 23.65 Jun-99 6217 1915 23542 13051 36593 10086 21.61 Jul-99 5591 1745 20409 25747 46156 9670 17.32 Aug-99 6486 2351 20680 22162 42842 10902 20.29 Total 640192 233217 2571079 675388 3246467 1140556 26.00 Number of Full Frame Images Received: 640192 Number of Observing Region Images Received: 3246467 Total: 3886659 Approximate Number of Shutter Moves/CCD Readouts: 6644483 NOTES: * The loss of images is mainly due to BDR overwrites, but there are also occasional DSN dumps which are lost. * It is common to have observing regions which contain more than 64 lines, which requires multiple exposures to make a single observing region image. This is why the number of shutter moves is larger than the number of images received plus those lost. Page 5 ENGINEERING SUMMARY TABLE Month Avg Dark Level # of Dark Spikes CCD Warmings Front Optical (DN) (e/sec) Over 48 Over 64 High / # Support Trans Temp /Days Temp (%) Jul-97 54.44 897.3 184518 20173 22.5 / 2 21.1 N/A Aug-97 54.06 883.1 188485 15549 20.1 N/A Sep-97 54.77 909.7 196501 17757 21.0 N/A Oct-97 54.85 912.8 198157 17857 21.5 N/A Nov-97 55.17 924.8 202153 18993 22.5 / 2 23.1 N/A Dec-97 55.51 937.6 206194 20219 21.9 N/A Jan-98 56.06 958.0 212189 22121 23.9 N/A Feb-98 55.94 953.7 209254 22122 23.8 / 2 22.6 N/A Mar-98 56.29 966.6 213519 23249 21.8 N/A Apr-98 56.44 972.1 214676 23890 20.8 N/A May-98 56.90 989.4 215651 26905 21.4 N/A Jun-98 57.11 997.5 216285 28223 20.1 N/A Jul-98 57.01 993.7 215499 27493 21.4 N/A Aug-98 57.36 1006.7 217355 29544 20.9 N/A Sep-98 57.43 1009.5 218520 29683 20.9 N/A Oct-98 57.59 1015.3 220504 30221 21.3 N/A Nov-98 58.17 1037.0 223755 34614 22.5 / 2 23.4 N/A Dec-98 57.86 1025.5 221918 32420 23.8 N/A Jan-99 58.74 1058.6 227503 38238 23.1 N/A Feb-99 58.44 1047.4 224002 36198 23.2 N/A Mar-99 59.26 1078.1 227900 43051 21.7 N/A Apr-99 58.82 1061.4 225973 38963 23.8 / 1 21.4 N/A May-99 58.68 1056.4 225385 37726 22.5 N/A Jun-99 59.40 1083.0 230091 42440 22.0 N/A Jul-99 59.78 1097.5 231236 46337 23.8 / 1 20.6 N/A Aug-99 59.40 1083.2 229426 43136 21.8 N/A NOTES: * The dark current calculations are using full half resolution 2.668 sec images not taken in during the SAA. The dark current rate assumes a "fat zero" of 30.5 DN and a gain of 100 e/DN. * The entrance filter failure of 13-Nov-92 eliminated the capability of taking optical images, so the optical transmission is not available after Nov-92. It also caused an increase in the dark current signal, however some of the increase shown here is an increase in the readout noise and is not a function of exposure duration. Page 6 PERSONNEL TRAVEL SXT Foreign Travel between 1-AUG-99 and 31-AUG-99 HUDSON 1-AUG-99 * 22-AUG-99 22 28-AUG-99 31-AUG-99 * 4 (total of 26 days) NITTA 28-AUG-99 31-AUG-99 * 4 (total of 4 days) ---------------------------------------------------------------- Grand Total of 30 days for 2 people NOTE: The "*" signifies travel that actually ends after 31-AUG-99 SXT Foreign Travel between 1-SEP-99 and 30-SEP-99 HUDSON 1-SEP-99 * 30-SEP-99 * 30 (total of 30 days) LEMEN 10-SEP-99 21-SEP-99 12 (total of 12 days) NITTA 1-SEP-99 * 24-SEP-99 24 (total of 24 days) SHIRTS 20-SEP-99 30-SEP-99 * 11 (total of 11 days) ---------------------------------------------------------------- Grand Total of 77 days for 4 people NOTE: The "*" signifies travel that actually ends after 30-SEP-99 Respectfully submitted, Thomas R. Metcalf Frank M. Friedlaender Page 7 ------------------------------------------------------------------------------- NASA REPORT DOCUMENTATION PAGE (IN LIEU OF NASA FORM 1626) --------------------|--------------------------|------------------------------- 1. REPORT NO. | 2. GOVERNMENT | 3. RECIPIENT'S DR-01 | ACCESSION NO. | CATALOG NO. --------------------|--------------------------|------------------------------- 4. TITLE AND SUBTITLE | 5. REPORT DATE Monthly progress report - for the month of | 10 September 1999 August 1999 |------------------------------- | 6. PERFORMING ORG | CODE: O/L9-41 -----------------------------------------------|------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- T. R. Metcalf | TION REPORT NO: F. M. Friedlaender | |------------------------------- -----------------------------------------------|10. WORK UNIT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS | Lockheed Martin Missiles and Space |------------------------------- Advanced Technology Center, O/L9-41, B/252 |11. CONTRACT OR GRANT NO. 3251 Hanover Street, Palo Alto Ca. 94304 | NAS8 - 40801 -----------------------------------------------|------------------------------- 12. SPONSORING AGENCY NAME AND ADDRESS |13. TYPE OF REPORT AND Marshall Space Flight Center (Explorer Program)| PERIOD COVERED Huntsville Alabama 35812 | Progress report for the month Contact: Larry Hill | of August 1999 |------------------------------- |14. SPONSORING AGENCY | CODE MSFC / AP32 -----------------------------------------------|------------------------------- 15. SUPPLEMENTARY NOTES ------------------------------------------------------------------------------- 16. ABSTRACT The SOLAR-A Mission is a program of the Institute of Space and Astronautical Science (ISAS), the Japanese agency for scientific space activity. The SOLAR-A satellite was launched on August 30, 1991, to study high energy phenomena in solar flares. As an international cooperative agreement, Lockheed, under NASA contract, is providing a scientific investigation and has prepared the Soft X-ray Telescope (SXT), one of the two primary experiments of the mission. --------------------------------------|---------------------------------------- 17. KEY WORDS (SUGGESTED BY | 18. DISTRIBUTION STATEMENT AUTHOR(S)) Solar-A, X-ray, CCD, | Space Science, Solar Physics ------------------------|-------------|----------|-----------------|----------- 19. SECURITY CLASSIF. | 20. SECURITY CLASSIF. | 21. NO OF PAGES |22. PRICE (OF THIS REPORT) | (OF THIS PAGE) | | None | None | 7 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office