Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-37334) (for the month of February, 1993) OVERVIEW 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 from Kagoshima Space Center (KSC) in Japan, and renamed Yohkoh. The purpose of this mission is to study high energy phenomena in solar flares. Under an international cooperative agreement, Lockheed, 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 by Lockheed in cooperation with the National Astronomical Observatory of Japan, and the Institute for Astronomy of the University of Tokyo. MAJOR ACTIVITIES IN THE MONTH << Solar Activity and Observation Planning >> During the week of 31-Jan to 6-Feb the solar activity was higher than the previous week. Thanks to the appearance of some active regions, the GOES background level was usually around C1. KSC data had two flares observed in flare mode. One was at 10:51 on 1 February and the other at 14:50 on 3 February. Both were observed in the new flare sequence that used only one filter (Be 119) so that we could see rapid variations if any in a same condition. Although neither of them was observed from the very early phase used to illuminate UV light on to CCD), at least the latter one showed significant change in a short interval. Partial frame images were mostly on bright regions in the eastern hemisphere. At the beginning of the week, there were two bright regions on the eastern limb, later named NOAA 7417 and 7416. NOAA 7417 was characterized by high loops, whereas NOAA 7416 was more compact and flare productive. NOAA 7418 was probably an emerging flux region, which grew rapidly. The Sun was more active during the week from 7-Feb to 13-Feb. It produced at least 4 M-flares and about 50 C-flares. SXT followed AR7420 for most of the week as it was the dominant region on the disk. It produced a series of compact, impulsive C flares associated with a small area of magnetic flux in Page 2 the moat that is near the leader spot. Larger flares seem to be associated with the gamma region in the trailing region of the spot group. It produced some fascinating sequences of full-resolution flare and quiet mode partial-frame images while the full-frame images have shown the complex structure of the larger and fainter loops connecting the various parts of the active region. Between 14-Feb and 27-Feb the sun produced at least 7 M-class flares and about 50 C-flares. During this period, the sun showed an interesting transition from an active Sun to a very much quieter configuration. The active regions all seemed to be simple bipoles but we have noted that some have reverse polarity, in fact an unusually high proportion. Another feature that these active regions have shared is a small XBP leading the leader spot. These have tended to be very active, often flaring and producing jets. One region produced a repeat of the 7 Dec 1991 flare/jet. Some of the velocities are in excess of 500 km/s and approach 1000 km/s in a few cases. Astro-D, now known as ASCA, was launched successfully on 20 February. The short delay in the launch was very advantageous to Yohkoh as it means there was almost no interference with Yohkoh operations. The two spacecraft will slowly move into phase with each other over the next year when we stand to lose about half of our KSC and DSN passes. << Joint Observing >> We supported the successful launch of the NRL rocket and obtained joint data. Unfortunately Yohkoh went into medium rate and we obtained images at a much lower rate than planned, however there should be ample data to make quantitative comparisons between the rocket-borne grazing-incidence X-ray telescope and SXT. << Scientific Activities >> Greg Slater has been working with Dr. R. White at HAO on solar irradiance problems and has supplied him with the X-ray flux as a function of time for the first 17 months of the mission. << Data Analysis Software >> Since there were many of the Hawaii and Lockheed pointing experts at ISAS for the science meeting, discussion was held about the problem of "de-jittering" SXT images. Jean-Pierre Wuelser demonstrated some new software that used HXA data to correct IRU data for x-ray image coalignment. A concentrated effort is being applied towards getting a single set of software released to be used for all alignment and registration applications. Page 3 << Instrument Operations and Health >> SXT has had a couple of SEU errors between 14-Feb and 27-Feb. The errors were recovered from quickly, but as the BCS has had similar problems it is suspected to be due to the phasing of the apogee of the Yohkoh orbit with the SAA. The errors, which are much less frequent than this time last year thanks to modification of the onboard software, are under investigation. We had several problems, mostly related to mainframe computers at ISAS. First, an SXT table was not transferred to KSC. Second, a routine to read Sirius database gave inconsistent results at different times. The bug was identified and it turned out that there were 14 such examples. In addition, we still sometimes failed to read Sirius database at all. The nameserver computer stopped working and we had difficulty sending e-mail from ISAS. Nariaki Nitta made a short manual in English for SSOC tobans, based on Japanese documents. The SXT-related work of SSOC tobans is not yet well defined. << Data Flow >> There was a problem with the network links to three of our workstations at ISAS. Greg Slater made a temporary fix while the Centrecom multiport repeater is being repaired. Archiving of the reformatted database to MO disks was started. For the next several weeks Gary Linford will work on archiving the Yohkoh data for the whole mission onto the MO disks which were provided by ISAS. << Papers and Conferences >> There was a 3-day Yohkoh science meeting held in Japan between 23-Feb and 26-Feb. There were many exciting results, many of them were far more quantitative than before showing a great deal of scientific progress. There were constructive and lively interchanges between the >100 participants from all over the world. Greg Slater gave a quantitative presentation on the scatter pattern seen in overexposed flare images. Gary Linford discussed temperatures of a small flare, the session chair had to call a halt to the deluge of questions. Karen Harvey gave a talk on XBP's based on the 9/10 Dec 92 XBP run. Nariaki Nitta won the most entertaining talk award given by Sakurai-san by somehow (successfully) linking AR flaring with bloodtype analysis. Keith Strong presented a talk on the bright footpoints seen in the earliest phases of flares. There were several presentations by the Hawaii group. One result, presented by Tom Metcalf, detailed the surprising result that the active-region heating seems unrelated to Page 4 large-scale currents. A paper was presented by Hara-san on the temperature of coronal holes. He had very methodically analysed some SXT images of coronal holes, finding temperatures of about 2 MK. Still the most confounding result from the SXT data is the confined bright emission at the tops of loops that was presented by Uri Feldman. The length of time that the brightness gradient is maintained is longer than seems plausible for just about any conceivable physical mechanism. Several interesting results were also presented by the other Yohkoh experiments. The BCS team showed data from a survey of many bright flares which show a surprisingly low value for the average upflow rates in flares. The WBS team showed some gamma-ray spectra from the 4 big flares that they have observed so far. HXT images are beginning to be used as commonly as SXT images in flares analysis now. The most pleasing aspect of the meeting was the way in which the data from different Yohkoh instrument observatories is beginning to be analysed as a whole rather than by an individual event or instrument basis. This is a direct result of the holisted for the Yohkoh software. << Miscellaneous >> The SXT project at LPARL employees two to three high school students who are selected from Palo Alto public high schools, usually at the end of their junior year. For several years Lockheed has worked with the Palo Alto School District to recruit students from math and science classes with the recommendation of school advisors to work with scientists and engineers at LPARL on a variety of tasks. Those selected are very motivated and capable students who generally possess a 3.5 to 4.0 GPA. They work full time during the summers and work 12 hours per week during the school year. On the SXT project the students are responsible for a several tasks including: making copies of the data tapes and sending them to the various Co-I institutes; generation of the long-term full-Sun laser video movie; writing of software to make color displays; preparation of color hard-copies; assisting the preparation of project financial statements. The students are often given specific tasks, usually to prepare data sets for further analysis. In the course of their tenure the students are exposed to a research environment and are involved in the analysis of data. They are trained to use computers, including some limited programming assignments. All the previous students from the SXT project have gone on to prestigious, four-year universities, often with the intention to major in a science, engineering or computer science field. Page 5 << Engineering Summary Table >> Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Sep-91 501 413 20914 3541 24455 5741 19.01 Oct-91 4095 2543 6389 12195 18584 3647 16.41 Nov-91 5276 2555 12173 14686 26859 10990 29.04 Dec-91 4834 3252 4940 16887 21827 6903 24.03 Jan-92 5544 3177 10084 5972 16056 6849 29.90 Feb-92 4868 2865 15449 9623 25072 13579 35.13 Mar-92 5910 2699 19236 2653 21889 10589 32.60 Apr-92 6751 3483 20157 5423 25580 12327 32.52 May-92 6783 3407 24535 4444 28979 14819 33.83 Jun-92 6417 3632 21648 12725 34373 14782 30.07 Jul-92 6345 3275 23941 10510 34451 14717 29.93 Aug-92 6572 2978 24207 11154 35361 13550 27.70 Sep-92 6087 2916 26832 20042 46874 15729 25.12 Oct-92 6743 2589 50985 14709 65694 23687 26.50 Nov-92 6658 2939 24416 14696 39112 12924 24.84 Dec-92 6775 2999 24253 6633 30886 12356 28.57 Jan-93 6888 3351 24067 4861 28928 13069 31.12 Feb-93 4836 2222 17374 16093 33467 8978 21.15 Total 101883 51295 371600 186847 558447 215236 27.82 Number of Full Frame Images Received: 101883 Number of Observing Region Images Received: 558447 Total: 660330 Approximate Number of Shutter Moves/CCD Readouts: 1204843 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. * Not all of Feb-93 data was available when the table was generated Page 6 Month Avg Dark Level # of Dark Spikes CCD Warmings Front Optical (DN) (e/sec) Over 48 Over 64 High / # Support Trans Temp /Days Temp (%) Oct-91 31.18 25.4 889 33321 10.5 78.6 Nov-91 31.06 21.0 651 34706 11.9 64.5 Dec-91 31.04 20.2 804 35175 14.0 52.6 Jan-92 31.15 24.2 1021 39160 0.5 / 2 14.9 38.4 Feb-92 31.32 30.9 1176 44654 14.3 31.8 Mar-92 31.47 36.5 1354 49535 14.8 25.1 Apr-92 31.44 35.2 1323 49325 23.8 / 4 14.6 22.8 May-92 31.65 43.1 1417 56822 14.4 20.1 Jun-92 32.11 60.3 2158 70647 -2.5 / 3 15.1 17.4 Jul-92 32.22 64.4 1852 79326 15.5 14.1 Aug-92 32.21 64.1 1922 77488 14.9 13.1 Sep-92 32.38 70.5 2062 84758 -1.2 / 3 15.9 12.2 Oct-92 32.64 80.3 2317 94956 16.8 11.5 Nov-92 36.06 208.5 5876 165111 18.0 11.0 Dec-92 42.58 452.8 17390 255840 17.9 N/A Jan-93 42.64 455.1 13388 261040 23.8 / 2 19.2 N/A Feb-93 N/A N/A N/A N/A 17.6 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 Travel for the month of February, 1993: HUDSON 1-FEB-93 * 11-FEB-93 11 19-FEB-93 28-FEB-93 * 10 (total of 21 days) LINFORD 1-FEB-93 * 10-FEB-93 10 17-FEB-93 28-FEB-93 * 12 (total of 22 days) NITTA 1-FEB-93 * 25-FEB-93 25 (total of 25 days) SLATER 1-FEB-93 * 26-FEB-93 26 (total of 26 days) STRONG 7-FEB-93 28-FEB-93 * 22 (total of 22 days) CANFIELD 6 (total of 6 days) WUELSER 21-FEB-93 27-FEB-93 7 (total of 7 days) HARVEY 7-FEB-93 28-FEB-93 * 22 (total of 22 days) KLIMCHUK 22-FEB-93 27-FEB-93 6 (total of 6 days) Planned SXT Travel for the month of March, 1993: BRUNER 23-MAR-93 31-MAR-93 * 9 (total of 9 days) HUDSON 1-MAR-93 * 31-MAR-93 * 31 (total of 31 days) LINFORD 1-MAR-93 * 18-MAR-93 18 25-MAR-93 31-MAR-93 * 7 (total of 25 days) NITTA 18-MAR-93 31-MAR-93 * 14 (total of 14 days) STRONG 1-MAR-93 * 11-MAR-93 11 18-MAR-93 31-MAR-93 * 14 (total of 25 days) HARVEY 1-MAR-93 * 1-MAR-93 1 (total of 1 days) Respect D. Morrison Frank Friedlaender Page 8 -------------------------------------------------------------------------------- UNIVERSITY OF HAWAII ACTIVITY REPORT (DR. R. CANFIELD) Our most important activities included support of YOHKOH operations and data analysis at ISAS, coordinated ground-based data acquisition at MSO, upgrading of the telescope optics of the IVM, collaborative analysis of YOHKOH/MSO data, and presentation of papers at the February YOHKOH science meeting and the Coordinated Data Analysis Workshop (CDAW) at ISAS. Hudson supported SXT operations at ISAS. Canfield spent most of January at ISAS, serving as SSOC toban for one week and presenting a seminar, while spending the remaining time on research. Operations support was provided by Koon, Nitta and Judd at MSO; solar activity was variable, weather rather poor, and the IVM was taken out of operation for replacement of the telescope secondary. Canfield, Hudson, de La Beaujardiere, Metcalf, and Wuelser participated in the YOHKOH Science meeting. Hudson presented Lemen's results on SXT calibrations; as well, he presented YOHKOH and CGRO observations of several slow long-duration events to demonstrate their nonthermal nature. Wuelser distinguished between thermal and nonthermal H-alpha and X-ray signatures of chromospheric evaporation during the early phase of the 15 November 1991 flare. Metcalf described the interesting lack of a relationship between MSO observations of electric currents and SXT observations of bright soft x-ray structures in AR 6952. Canfield showed that the filament eruption before the Nov 15 flare began to move long before any evidence of heating in the Ca II K line. Leka worked with van Driel-Gesztelyi and Anwar on observations of magnetic flux emergence in AR7260; the results were presented by van Driel-Gesztelyi. Canfield, Hudson, de La Beaujardiere, Metcalf, and Wuelser participated in the CDAW on the 1991 Nov 15 and Oct 24 flares. Working with Kurokawa, Canfield found clear evidence for emerging flux before the Nov 15 flare. Working with Masuda, Metcalf and de La Beaujardiere placed the HXT observations of the Oct 24 flare in a magnetic and chromospheric context. Working with Sakao, Kawabata, Hudson, and McTiernan, Wuelser calculated the H-alpha energetics for both flares, and made comparisons of the SXT, GRS, GOES, and HXT observations. Hudson applied his new GOES reduction software to the two flares; comparison with McTiernan's reductions of SXT temperatures and emission measures resulted in reasonably good agreement, but interesting discrepancies. As a contribution to the general SXT data analysis effort, Wuelser provided new software to remove the spacecraft jitter from SXT images and Hudson finished his GOES reduction software. Page 9 Mickey and Leka installed the new secondary mirror in the IVM telescope and interferometrically tested the telescope performance. The telescope now introduces a rms wavefront error of less than a tenth-wave, and sub-arcsecond images have been obtained under good atmospheric conditions. A minor change to the IVM software has been made to permit sequences of magnetograms, at intervals of about six minutes. The instrud H-alpha polarization data from two flares during the October 1992 observing period. Preliminary indications are that there are small areas, near the ends of the H-alpha flare ribbons, which show linear polarization approaching ten percent. It is believed that this polarization may be the signature of low energy protons in the flares. PLANS FOR MARCH AND APRIL Hudson and Metcalf will attend the CGRO workshop on high-energy flare studies to present YOHKOH observations and MSO observations respectively. Hudson will work on the "impulsive footpoints" discovery in the SXT data. With Sakao, he will incorporate into this study HXT imaging, which is now available for several of the impulsive-footpoint events. Wuelser plans to extend his analysis of chromospheric/coronal flare dynamics and energetics to a larger set of events. He will also work on an improved MSO white light telescope for a more accurate co-registration of MSO and YOHKOH images. Mickey and Leka will get the IVM back into full operation, with improved imaging. Leka will travel to Japan in April, to work at ISAS for two weeks with van Driel-Gesztelyi on a survey paper about flux emergence in AR7260. Mickey will concentrate on IVM data acquisition and reduction, to ensure that any remaining instrumental problems can be promptly addressed, and to develop the most effective analysis procedure. Metcalf plans to finish the AR6952 paper on currents and soft X-ray structures and to work further on the H-alpha polarization data, gathering supporting YOHKOH data. Jiao and Metcalf will finish their study of chromospheric magnetic fields. Metcalf will also analyze magnetic field data requested by colleagues at the YOHKOH science meeting. Canfield will work on the preflare phenomena associated with the Nov 15 flare. Page 10 -------------------------------------------------------------------------------- UNIVERSITY OF CALIFORNIA AT BERKELEY The work during this reporting period (Jan-Feb, 1993) consisted of analysis and interpretation of data, and preparation and presentation of papers. McTiernan presented a paper on the temperature and density structure of flares, based on the analysis of 46 flares from Oct. 1991 to Feb. 1992 at the Yohkoh Science Meeting held in Sagamihara, Japan from Feb. 23-25, 1993. He will be at ISAS until Mar. 13, working on the preparation of the manuscript of the above-mentioned paper, and will attempt to include the effects of the wavelength dependent . This will help in determination of temperature and density in flare loops. McTiernan is also working on a project that will enable the SXT filters to be treated as if they were spectrometer channels, to enable temperature and emission measure determination using more that two filters, and also combined SXT-HXT spectra. This work will also be useful when the SXS response functions are on-line. Work by Mctiernan and Kane regarding the comparison of thick-target electron beam models with HXT results, is continuing. McTiernan is currently working on a computer code that will calculate the spatial, time and angular dependence of thick-target bremsstrahlung from electron beams for various geometries. This is a long-term project which will hopefully be completed this year. Slocum, a student at UCB, and Kane are studying gradual hard X-ray sources observed by the Yohkoh WBS and HXT. The production of survey plots of the WBS data is nearly complete. Page 11 -------------------------------------------------------------------------------- STANFORD UNIVERSITY (DR. P. STURROCK) During the past two months, Jim Klimchuk, Peter Sturrock, George Roumeliotis, Taeil Bai, Lisa Porter, and Rich Fuller attended the Solar Neighborhood Meeting held on February 12 at the Space Science Laboratory of the University of California, Berkeley. The following presentations were given: "Deconvolution of SXT Images" by Roumeliotis, "Asymptotic Behavior of Force-Free Magnetic Fields" by Sturrock, "Flare Periodicities During Cycle 22" by Bai, and "Wave Heating of the Solar Corona" by Porter. Klimchuk attended the Yohkoh Science Meeting held during February 23-25 at the Kokumin-Seikatsu Center in Fuchinobe, Japan, where he presented a talk entitled "Coronal Mass Ejections Observed by Yohkoh and the Mauna Loa Coronagraph." He also visited ISAS for two days following the meeting to collaborate with other Yohkoh scientists. During the next two months, Klimchuk will continue to study coronal eruptions using SXT data, and he hopes acquire MLSO coronagraph data for comparison. Roumeliotis will refine his deconvolution techniques for SXT images and will investigate the cross-sections of coronal loops using the processed data. Porter will begin a study to determine the relationship between loop pressure and loop length, which has important implications for the height distribution of coronal heating. Page 12 -------------------------------------------------------------------------------- SOLAR PHYSICS RESEARCH CORPORATION (KAREN L. HARVEY) Activity these last two months has focussed on several areas: (1) Update of bibliography of SXT/Yohkoh papers to include those recently published in PASJ, volumn 44. (2) During a three-week visit (Feb 9 to March 1) to ISAS in Japan, analysis of data obtained during collaborative observing program between the SXT on Yohkoh and the NSO/KP magnetograph. High temporal and spatial resolution PFI observations of X-ray Bright Points (XBPs) were obtained to determine the scale ofations. SXT observations consisted of 2 x 2 full-resolution map, 5x5 arcmin area, a time resolution of 32 seconds, and maximum exposure of 5 seconds. Coordinated magnetic field observations were taken by NSO/KP spectromagnetograph at a cadence of 7.5 minutes and spatial resolution of 2.3 arc-sec. These observations were obtained by Yohkoh SXT instrument and the NSO/KP magnetograph on December 9 and 10, 1992. The analysis to date has concentrated on the data acquired on December 9, the best of the days in terms of coverage and clear weather at Kitt Peak. In total, 19 XBPs were observed in the field of view. All were associated with magnetic bipoles; 4 were static, 12 were cancelling, and 3 were emerging. 17 of the XBPs showed rapid intensity variations; the strongest was an increase of 200 counts, a factor of 2 increase, within 32 seconds. The intensity variations occurred over a significantly shorter time than observed changes in the associated magnetic field. It is concluded that XBP are the result of reconnection of magnetic fields, and not specifically to the cancellation or emergence of magnetic flux. Based on the results of this study, we propose changes in future collaborative programs to improve the time resolution of the SXT partial frame images and the simultaneous magnetograms. Additional observational support from Hawaii, Japan, and China have been planned to extend the magnetic field time base. The appended proposed observing program has been submitted and approved by S. Tsuneta and L. Acton. The results from this analysis were presented at a Yohkoh meeting at ISAS in February 1993. (3) Continued discussions with Keith Strong on next phase of study of BPs. This includes the development of a detailed plan of research using current data to sample XBPs during the more than one year of operation of Yohkoh. We are considering the specific properties and methods of analysis of the data to determine time variation in the counts of BPs, their association with magnetic fields and He I 10830 dark points, lifetimes, temperatures, temporal variations, solar rotation rates. Page 13 (4) Coordinating the analysis of the NSO/Kitt Peak full-disk magnetograms and He I 10830 spectroheliograms for specific filamenth Strong, and David Sime (e.g. the 25 February 1992 and 24 January 1992 events) and coronal holes with G. Slater, L. Acton, P. Bornmann, T. Hara, H. Hiei, M. Kubo, G. Linford, P. McIntosh, and T. Takahashi. Page 14 -------------------------------------------------------------------------------- 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 | March 10, 1993 February 1993 |-------------------------------- | 6. PERFORMING ORGANIZATION | CODE: O/91-30 -----------------------------------------------|-------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- M. D. Morrison | TION REPORT NO: F. M. Friedlaender | |-------------------------------- -----------------------------------------------|10. WORK UNIT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS | Lockheed Palo Alto Research Labs B/252 |-------------------------------- Solar & Astrophysics Laboratory O/91-30 |11. CONTRACT OR GRANT NO. 3251 Hanover Street, Palo Alto Ca. 94304 | NAS8 - 37334 -----------------------------------------------|-------------------------------- 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 | of February, 1993 |-------------------------------- |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 | 14 | ------------------------|------------------------|-----------------|------------ For sale by: Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402-0001 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. Delivered From Subject Lines 2 Mar 10 15:15 LACTON SXT Monthly Report for February, 556 <<< END >>> Thursday, Mar 11, 1993 12:23 PM PST