Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-00119) (for April 2001) 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 The program continues to operate without any issues. Preparations for the Senior Review were certainly the high point for the month. SOLAR ACTIVITY Solar activity in April ranged from "incredibly high" to merely "high". In early April, activity was dominated by AR9393 which, among many other flares, produced the X22 event on April 2. This flare was the largest ever recorded by space-based instrumentation. During the first week of April, before AR9393 and its naked-eye sunspot completed its disk passage, there were five X-class flares and 14 M-class flares. Amazing! AR 9393 achieved a total spot area of 2440 millionths on March 30. After the passage of AR9393, AR9415 took over and produced three more X-class flares and three more M-class flares by mid-month, including an X14 event on April 15. The Yohkoh GRS instrument observed gamma-radiation up to at least 10 MeV in this event. The spectrum can be fit by a power law up to about 7 MeV and exhibits a break above that energy. Commenting on the very high level of activity, Pat MacIntosh (Heliosynoptics, Boulder, Colorado) noted that "Only seven active regions in the past 30 years exceeded the flare output of Region 9393 or Region 9415! It is remarkable that these two regions were so perfectly equivalent in flare output and occurred on the same solar rotation at longitudes 160 degrees apart and in opposite solar hemispheres. Such symmetry in great flaring regions also occurred in July 1982." Page 2 After mid April, the Sun calmed down a bit though activity was still high. There were no further X-class flares, but ten M-class flares, mostly from AR 9433, were recorded. The most interesting event was was the "slow LDE" of April 26, which included an impulsive component at the almost-X level of M7.8. This event featured a sigmoid dimming and a Bastille-like arcade. CAMPAIGNS There were no formal campaigns during April, but joint observing of AR9393 and AR9415 with many observatories on the ground and in space will surely yield a wealth of information on these incredible active regions. SCIENCE Yohkoh observed the powerful X22 flare on April 2. The most intriguing feature of this remarkable event is that this was a very compact flare. The small area of the flare was unexpected given that this was the most powerful solar flare ever observed in X-rays. Many powerful flares occur in large arcade structures, such as the remarkable Bastille Day event observed so well with Yohkoh and TRACE. A day after the X22 event, there was an X1.2 flare in a completely different active region. Thus, we learn that distinct active regions can make major flares almost simultaneously. This fact has been debated. What's happened is consistent with the basic idea that the emergence of magnetic flux from the photosphere, rather than the collapse of the coronal magnetic field, drives flares most directly. Acton completed a first-order analysis of the SXT scattering wings. The scattering slope is hard to determine with precision because of imperfect pre-flare subtraction and coronal changes (coronal dimming, ejecta, etc.) initiated by the flare itself. A slope of -2.0, as proposed by Hara-san many years ago, appears to be the best compromise. To within experimental errors the slope in the rays is also -2.0 and the intensity is 3 times less than between the rays. This work is so far based upon thin-filter starbursts taken before the first SXT entrance filter failure. Limited study of thick-filter starbursts indicate that their scattering slope may also be represented by -2.0. However, the jury is still out on relative scattering intensity vs. wavelength, temperature, and filter thickness. Especially for the thin filters, where the entrance filters represent a significant opacity, the scattering wings become non-symmetric around the image as these filters have sequentially failed. McKenzie continued working with B. Kliem and W. Curdt of SUMER, on analysis of a C flare from 6-nov-99. SXT sees expansion of one loop, while the rest of the region appears not to respond -- foreground/background confusion is a likely explanation; but SUMER's blobs and interesting line shifts imply that "cool and hot plasma showed correlated line shifts and line widths, moving with about equal but opposite velocity during a short interval." Page 3 Nitta started analyzing data for the 18-Mar-00 flare, which was observed by Yohkoh and TRACE. Specifically, the flare occurred while TRACE was in a high-cadence mode at 1600 A. He compared 1600 A light curves of what appear to be footpoint sources with HXT light curves. The agreement was quite good for some peaks but not all. The plan is to compare the UV light curves with spatially-resolved HXT light curves. PUBLICATIONS Submitted: Aschwanden,M.J. and Alexander,D., "Flare Plasma Cooling from 30 MK down to 1 MK modeled from Yohkoh, GOES, and TRACE observations during the Bastille-Day Event (2000 July 14)" Aschwanden,M.J., "An Evaluation of Coronal Heating Models based on Yohkoh, SoHO, and TRACE Observations" Accepted: Aschwanden,M.J., Poland,A.I., and Rabin,D. 2001, Ann. Rev. Astron. Astrophys. 39, (in press). Published: Aschwanden,M.J. and Acton,L.W. 2001 ApJ 550, 475-492 "Temperature tomography of the soft X-ray corona: measurements of electron densities, temperatures, and differential emission measure distributions above the limb" Aschwanden,M.J., Schrijver,C.J., and Alexander,D. 2001 The Astrophysical Journal 550, 1036-1050 "Modeling of coronal EUV loops observed with TRACE : I. Hydrostatic solutions with nonuniform heating" 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 April were 166081 accesses and 12,972 Mbytes transferred for the SXT website and 372466 accesses and 10,711 Mbytes transferred for the YPOP website. 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: Page 4 SXT Error 02-Apr-01 Pass 1: 010402-0928 Recovered in the same pass. SXT Table Upload Error 10-Apr-01 Pass 4: 010410-0825 Table retransmitted in the same pass. SXT Bit Map Error 11-Apr-01 Pass 1: 010411-0515 Recovered in the same pass. SXT Bit Map Error 13-Apr-01 Pass 1: 010413-0618 Recovered in the same pass. SXT Bit Map Error 20-Apr-01 Pass 1: 010420-0205 Recovered in the same pass. SXT Bit Map Error 24-Apr-01 Pass 1: 010424-0102 Recovered in the same pass. SXT Bit Map Error 25-Apr-01 Pass 1: 010425-0102 Recovered in the same pass. SXT Bit Map Error 30-Apr-01 Pass 1: 010430-1443 Recovered in the same pass. Page 5 DATA FLOW Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Feb-99 601932 222169 2421187 585803 3006990 1078246 26.21 Mar-99 6807 1844 24721 12354 37075 10064 21.35 Apr-99 6715 1371 25113 4179 29292 7791 21.01 May-99 6459 1807 35467 12092 47559 13757 22.44 Jun-99 6217 1915 23542 13051 36593 10086 21.61 Jul-99 5591 1745 20409 25747 46156 9670 17.32 Aug-99 6827 2503 21725 23361 45086 11844 20.80 Sep-99 5768 2011 21890 3434 25324 10846 29.99 Oct-99 5768 2308 22994 10487 33481 11517 25.59 Nov-99 7552 3425 20754 18772 39526 11974 23.25 Dec-99 7488 2791 22047 5354 27401 10663 28.01 Jan-00 5426 1736 19802 4040 23842 8958 27.31 Feb-00 6533 2052 21801 7017 28818 8982 23.76 Mar-00 6447 2007 22692 21914 44606 11192 20.06 Apr-00 6412 2100 31195 7214 38409 13438 25.92 May-00 6995 1556 28175 14961 43136 8967 17.21 Jun-00 7043 1722 24413 16369 40782 8690 17.57 Jul-00 6674 1920 23505 31739 55244 10235 15.63 Aug-00 9623 1996 20925 1197 22122 6577 22.92 Sep-00 8835 2240 22233 5764 27997 8307 22.88 Oct-00 6348 1524 23309 6629 29938 7916 20.91 Nov-00 6525 1639 20087 10318 30405 6972 18.65 Dec-00 6585 1918 20718 5422 26140 8071 23.59 Jan-01 5610 1231 20469 3161 23630 7317 23.64 Feb-01 6917 1497 25366 1144 26510 7871 22.89 Mar-01 6851 1272 26315 17139 43454 9470 17.89 Total 769948 270299 3010854 868662 3879516 1319421 25.38 Number of Full Frame Images Received: 769948 Number of Observing Region Images Received: 3879516 Total: 4649464 Approximate Number of Shutter Moves/CCD Readouts: 7910040 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 6 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 (%) 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 21.6 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 59.39 1083.0 229319 43067 21.7 N/A Sep-99 60.04 1107.3 231585 49084 21.8 N/A Oct-99 59.66 1092.9 229735 45263 22.8 N/A Nov-99 59.90 1102.0 231288 47102 23.0 N/A Dec-99 60.55 1126.3 233523 53920 22.5 / 2 25.3 N/A Jan-00 60.27 1115.9 233820 50214 23.4 N/A Feb-00 60.93 1140.6 235079 56836 23.8 N/A Mar-00 60.72 1132.8 234174 54661 22.9 N/A Apr-00 61.10 1147.0 235252 58348 22.2 N/A May-00 61.00 1143.1 234569 57445 21.2 N/A Jun-00 61.19 1150.3 235622 58946 22.8 N/A Jul-00 61.96 1179.3 238114 66905 19.3 N/A Aug-00 61.27 1153.4 236108 59965 56.9 / 2 21.7 N/A Sep-00 61.08 1146.2 235644 58449 22.1 N/A Oct-00 61.44 1159.5 237142 61667 23.1 N/A Nov-00 60.99 1142.7 235849 57271 24.2 N/A Dec-00 61.59 1165.2 237454 63656 23.8 / 2 21.8 N/A Jan-01 61.64 1167.3 238962 62922 22.2 N/A Feb-01 61.84 1174.6 239218 65324 23.5 N/A Mar-01 61.89 1176.7 239128 65898 23.1 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 7 PERSONNEL TRAVEL SXT Foreign Travel between 1-APR-01 and 30-APR-01 BARTUS 1-APR-01 * 30-APR-01 * 30 (total of 30 days) CANFIELD 28-APR-01 30-APR-01 * 3 (total of 3 days) HUDSON 1-APR-01 * 19-APR-01 19 26-APR-01 30-APR-01 * 5 (total of 24 days) TAKEDA 1-APR-01 * 30-APR-01 * 30 (total of 30 days) ---------------------------------------------------------------- Grand Total of 87 days for 4 people NOTE: The "*" signifies travel that actually ends after 30-APR-01 SXT Foreign Travel between 1-MAY-01 and 31-MAY-01 BARTUS 1-MAY-01 * 31-MAY-01 * 31 (total of 31 days) CANFIELD 1-MAY-01 * 09-MAY-01 9 (total of 9 days) HUDSON 1-MAY-01 * 10-MAY-01 10 (total of 10 days) NITTA 15-MAY-01 27-MAY-01 13 (total of 13 days) TAKEDA 1-MAY-01 * 24-MAY-01 24 (total of 24 days) ---------------------------------------------------------------- Grand Total of 87 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-MAY-01 Respectfully submitted, Thomas R. Metcalf Frank Friedlaender Page 8 ------------------------------------------------------------------------------- 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 May 2001 April 2001 |------------------------------- | 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 - 00119 -----------------------------------------------|------------------------------- 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 April 2001 |------------------------------- |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 | 8 | ------------------------|------------------------|-----------------|-----------