New XPOW: Solar Cycle 24
New XPOW: Coronal Mass Ejection on April 4th, 2014
New XPOW: Current Sheet Structure on the Limb
New XPOW: Dark Spike Amid Flaring Loops
The XRT DVDs are Back in Stock!
We have received a new supply of Space Science Careers: Building Hinode XRT, A Space X-Ray Telescope. When students think of NASA, they're likely to imagine astronauts and engineers without appreciating the much wider spectrum of careers that make spaceflight possible. This DVD tells the stories of many people involved in the making of XRT, along with providing some information on the telescope and its science. It's a great resource for high school students, guidance counselors, or anyone looking to increase career awareness. Click here to request a (free) copy.
New XPOW: Emerging Active Regions
New XPOW: X1.3 Flare with Interesting Structure on April 25th, 2014
New XPOW: Beautiful Candle Flame Cusp on the Disk
Big News! XRT-CO Adam Kobelski (MSU) successfully defended his PhD thesis!
Adam successfully defended his thesis on April 29, 2014: "Empirical Studies on the Initiation of Impulsive Heating in Coronal Loops." He will be starting a postdoc job in May at the National Radio Astronomy Observatory in Green Bank. Congratulations from the Hinode / XRT Team, Dr. Kobelski!
New XPOW: Solar Eclipse of April 29th, 2014
New XPOW: Flares and Flowers
New XPOW: X-Flare & EUV Wave on March 29th, 2014
New XPOW: Coronal Rain Extinguishes Active Region
New XPOW: Lovely Eruption & M-Flare from November, 2011
Important Calibration Software Update
Significant improvements have been made to the XRT_PREP code, which includes several new features in addition to minor bug fixes. Users should ensure that their SSW IDL libraries are up-to-date.
The UNCERT_MAP keyword has been added to provide an array of photometric errors due to calibration uncertainties (e.g., uncertainty in the dark subtraction, Fourier filtering, vignetting correction, exposure time, etc.). For details, see Kobelski et al. 2014, Solar Physics, in press; arXiv:1312.4850. The error array provides a basal estimate of uncertainty in the XRT data. Note that photon noise errors are not included, as these depend on the detailed thermal structure of the target, since XRT is a broadband detector.
The DESPIKE_DESPOT keyword has also been introduced to provide a cosmetic correction for contamination spots and dust on the CCD (using the XRT_SPOTCOR subroutine), in addition to particle hits. The spot correction uses thin plate splines (in most cases) to smoothly interpolate between boundary pixels outside of the given spot/dust area. It is highly recommended that the user employ this in conjunction with the GRADE_MAP keyword, which generates a pixel grade map so that the location of spots and dust can be identified. Note that this correction is purely cosmetic; pixels affected by dust and/or spots should not be used for quantitative analysis. A new despiking code (XRT_DESPIKE2), which better avoids over-correcting the data, has also been introduced.
The dust on the CCD has been growing between CCD bakeouts and shrinking after bakeouts since May of 2012, suggesting that contamination is starting to adhere to the dust temporarily. The cosmetic correction code also adjusts (approximately) for the time-dependent dust size. A new catagory of pixel grade, dust growth pixels, has been added to the output of XRT_PIXEL_GRADE.
Usage notes can be found in the XRT_PREP program header (and the headers of related routines). Detailed information is also provided in an updated version of the XRT Analysis Guide.
New XPOW: Filament Eruption with Unusual Twisting Motions
New XPOW: 112 Hours of Full-Sun X-Ray Images
New XPOW: Mysterious Flare-Ribbon-Like Structure
XPOW Archive Upgrade
The XPOW Archive has been upraded to be more easily searched. Each XPOW entry now also includes "keywords" that can be used to find related posts by querying the archive.
New XPOW: Sigmoids on Parade!
New XPOW: Polar Aurora
New XPOW: Cutest. Loop. Ever.
New XPOW: X-Ray Sun Two-Month Mashup
New XPOW: Full-Sun Images in Three Temperature Ranges
New XPOW: X1.1 Flare with CME on November 10th, 2013
New XPOW: Heart-shaped productive Active Region 11875
New Observation Resources!
The XRT Team has released two new resources for browsing XRT data. First, we have a revamped synoptic gallery. All of XRT's twice-daily full sun images are on display, and starting in June of 2013, each image is a composite of 3 exposures (long-medium-short) instead of 2. This provides a more lovely showing of the broad dynamic range the sun is currently displaying in its maximum activity phase.
Next, we've got the XRT Flare Catalog. The catalog includes basic information for all the flares that have occurred during the Hinode mission, along with summaries and preview movies of XRT's observations for each event. Links to both resources can be found under the "Data" tab in the sidebar and under "Observations" on the Mission Ops page.
New XPOW: Solar Eclipse of November 3rd, 2013
Calibration Update: The calibration of the instrument response functions has been updated, and the XRT response software in SolarSoft has also been updated accordingly (e.g. make_xrt_wave_resp.pro, xrt_teem.pro, xrt_eff_area.pro, etc.). The change adjusts some of the filter thicknesses to reflect the analysis of Narukage et al. 2013. As a result, the estimated effective areas of those filters (med-Be, med-Al, thick-Be, & thick-Al) have changed.
Click here for a plot of the updated temperature response functions (dotted lines indicated the previous calibration).
The new calibration files have been made available in SolarSoft. Please ensure that your SSW IDL libraries are up to date. See program headers and/or the XRT Analysis Guide for documention, and please direct questions and bug reports to xrt_manager [at] head [dot] cfa [dot] harvard [dot] edu.
New XPOW: More Flares from AR 11882!
New XPOW: M-Flares with CMEs on October 26th & 27th
New XPOW: Sigmoid Eruptions on August 7th, 2013
New XPOW: B Flare on September 23rd
Congratulations from the XRT Team to Lucas Tarr and Will Hanneman for recently completing their respective theses. The newly minted Dr. Tarr successfully defended his PhD dissertation on "Energetic Consequences of Flux Emergence", and Mr. Hanneman completed a master's thesis on the "Thermal Structure of Current Sheets and Supra-Arcade Downflows".
XRT Spotlight: Head over to the Bad Astronomy blog at Slate for an article by Phil Plait on XRT eclipse observations from last May.
New XPOW: Slow CME with Supra-Arcade Downflows
New XPOW: M Flares and Sigmoid Sea Creatures
New XPOW: Tiny Active Region Bright Point
New XPOW: Flaring Loops in Active Region 11755
New XPOW: Sigmoid Dynamics from April 20-22, 2013
New XPOW: M5.0 Flare of May 22nd, 2013
New XRT paper: The paper "Indeterminacy and instability in Petschek reconnection" by Forbes, Priest, Seaton, and Litvinenko has been accepted for publication in Physics of Plasmas.
In this paper, two puzzling aspects of Petschek's model for fast reconnection are explained. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. The authors found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity not exist, the authors obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate.
New XPOW: Three X-Flares in 24 Hours!
New XPOW: Sigmoid Eruption on March 15th, 2013
New XPOW: Limb CME on Feb 15th, 2013
New XPOW: Coronal Cavity with Bright Core
New XPOW: Plasma Flows Along Coronal Loops
New XPOW: Happy Valentine's Day! UPDATE: XRT's valentine has been featured in a PopSci article, as Wired's Space Photo of the Day, and in a collection of astro-valentines compiled by Slate.
New XRT paper: The paper "Turbulent Dynamics in Solar Flare Sheet Structures Measured with Local Correlation Tracking" by David E. McKenzie has been accepted for publication in The Astrophysical Journal.
In this paper, motions in flare plasmas are monitored with Local Correlation Tracking (first time LCT has been used in the corona, maybe?). The velocity field of the plasma is determined, and from that a vorticity can be inferred. The paper demonstrates that recent developments in high-resolution, high-cadence imaging of the corona make it possible to study turbulence in the flare plasma. Turbulence has long been the domain of spectroscopy, where turbulence is inferred from nonthermal broadening of emission lines. Such 1-dimensional studies (i.e., velocities along the line of sight) have been all that was available. The imagery from XRT and AIA bring two additional spatial dimensions into play, and combination of the imagery with spectroscopy offers to complete the set. The reason it matters is this--- turbulence creates small length scales, and small length scales enable reconnection. In the words of the Heliophysics Roadmap, it's all about "the microphysics of magnetic reconnection by determining the kinetic processes responsible".
Although some dynamic activity was seen in other parts of the eruptive structure, the most notable feature was apparent rotation in the southernmost part of the extended coronal structure, immediately above the limb. The LCT allows the velocity field to be mapped, and then one can explore the plasma motion via either Eulerian or Lagrangian techniques. As an example, the vorticity has been calculated in this rotating feature (context and vortex map).
New XPOW: Fifteen Active Regions in One Image
New XPOW: C-Flare from Sigmoidal AR 11608
New XPOW: Long-Duration B-Flare from AR 11598
New XPOW: Sweeping Active Region Jet
New XPOW: X-Ray Bokeh
New XPOW: Rolling Void in AR 11563
Press coverage: Wired Science has an article entitled 5 Years of Incredible X-Ray Explosions From the Sun, which features an XRT video.
New XPOW: Solar Eclipse of November, 2012
New XPOW: Massive Filament Eruption from 2012/08/31
New XPOW: C-flare on Sept 27, 2012 (Filament Eruption)
Calibration event: XRT will be running a 72-hour CCD Bakeout, starting Tuesday, Oct. 9 (UT). There will be no science data taken during this time period.
Monthly Science Highlights: Each month we highlight recent XRT science papers. A PDF summary of the highlights is available. The papers themselves are ADS-linked below (when possible):
New XPOW: Synoptics Surrounding Sympathetic Filament Eruptions
New XPOW: 5.5 Years of XRT Synoptic Observations
New XPOW: Beautiful Candle Flame Cusp on the Limb
New XPOW: Filament Eruption with Supra-Arcade Downflows
New XPOW: X1.4 Flare of July 12, 2012
New XPOW: July Fireworks
New XPOW: High Cadence Flare Response with Long/Short Exposure Composites
New XPOW: The Emergence of Active Region 11512
New XPOW: Eruptive Flare with High-Cadence Response (2012/04/30)
New XPOW: The Transit of Venus
New XPOW: Wandering Field Lines During Filament Eruption
New XPOW: Solar Eclipse of May 20th, 2012
New XPOW: Supra-Arcade Downflows After Long Duration B-Flare
New XPOW: Hot Non-Potential Core in AR 11433
New XPOW: X-Points, Loop Expansions, and Cusp Loops
New XPOW: Possible Slip-Running Reconnection on 2012/03/25
Monthly Science Highlights: Each month we highlight recent XRT science papers. A PDF summary of the highlights is available. The papers themselves are ADS-linked below (when possible):
New XPOW: X-Ray Jet on 2012/03/16
New XPOW: Three X-Flares in Two Days from AR 11429
Conference Announcement: The Hinode 6th Science Meeting will be held in St. Andrews, Scotland, on August 13--17, 2012. The deadline for abstract submission is 30 June 2012. The deadline for registration is 30 June 2012.
New XPOW: Supra-Arcade Downflows Post X-Flare (2012/01/27)
Breaking News! XRT-CO Antonia Savcheva (BU) has passed the oral part of her PhD comprehensive exams.
We expect her thesis to be done in about a year from now. Congratulations from the Hinode / XRT Team, Antonia!
Monthly Science Highlights: Each month we will highlight three recent XRT science papers. A summary of the papers is given HERE . The papers themselves are ADS-linked below:
New XPOW: Highly Flare Productive AR Complex - 2012/01/22 Synoptic
Conference Announcement: The Hinode 6th Science Meeting will be held in St. Andrews, Scotland, on August 13--17, 2012. (We will announce a meeting website when one becomes available.)
New XPOW: Can you spot Comet Lovejoy?
Operational announcement: Regarding the MDP bit-error of 2011-December-7:
The MCU reset related to the MDP 2-bit error recovery was successfully performed. XRT can resume normal observations on Saturday evening (JST).
Operational announcement: A bit error has been detected in the MDP (Main Data Processor of the spacecraft). This happens occasionally, and the recovery is routine. However, there won't be any observations during the Thursday timeline period. Observations are expected to resume on Saturday evening (JST).
New XPOW: The Partial Solar Eclipse of 2011/11/25
2011 Flare catching statistics: Kathy Reeves has compiled some statistics on XRT's success rate on catching large (X- and M-class) flares in calendar year 2011, so far. The presentation will be made to the Hinode Science Working Group Meeting on Oct. 10. Here are a few:
Education / Public Outreach: XRT E&PO DVD now available free upon request:
The Hinode/XRT Team has put together a DVD product called The XRT
Education & Public Outreach DVD: Space Science Careers: Building
Hinode XRT, A Space X-ray Telescope. This package is available
free upon request.
Product order form
From the product description:
"Space Science Careers: Building Hinode XRT, A Space X-Ray Telescope is a resource for high school guidance counselors and others who provide career awareness information to high school students. The goal of Space Science Careers is to introduce students particularly those who might be interested in technical careers to the diversity of career opportunities at NASA and in the space industry...
"Space Science Careers embeds career awareness in video clips that document the construction of an X-ray telescope... that was launched into Earth orbit on the Hinode satellite on September 23, 2006. The resource provides students with a unique window into the workplace and an unscripted view of workers collaborating and solving problems as they attend to their specialties."
Education / Public Outreach: XRT Team Member Kentaro Yaji-san sends us this news:
Dear all This is Kentaro Yaji. Thank you for everybody efforts for HOP173 observations. This highly encouraged the high school students. The following is the homepage for HOP173 EPO campaign observation Sorry in Japanese. http://www.rikkyo.ne.jp/web/yaji/hinode/hop173/ The title of this page represents "Let's observe the sun with Hinode!" I don't sufficiently update the images taken by high school students. But there is a list of high school in the last part of the homepage. If you click the high school name, you might be see some solar images. In the following, the observation results of last year are previewed. http://www.rikkyo.ne.jp/web/yaji/hinode/hop173/hop173_preview.html Regards, Thank you. ------------------------ Rikkyo University Kentaro Yaji
Operational announcement: Filter wheel 1 (FW1) has been returned to automatic control mode. During spacecraft eclipse season, FW1 is put into a manual control mode to mitigate against possible lock-ups. Now that eclipse season has ended, FW1 has been returned to a mode where all of its filter positions can be freely used by the observing tables.
Data gap: XRT temporarily stopped taking data around 11:17 UT on July 28. It has been determined that there was an error made in a table upload. Apart from missing a few days' worth of data, there have been no negative consequences of this error, and there was never any risk. Observations resumed around 10:38 UT on August 4.
Job Announcement: The Solar and Stellar X-ray Group at SAO is hiring for an Astrophysicist position. Details on the job, qualifications and the application process can be found here: SAO Job#11-46. The application deadline is being extended to July 31.
The abstract deadline for the Hinode-5 Science Conference has been extended to August 15.
Hinode-5 (The Fifth Hinode Science Conference) will be held in Cambridge, MA, October 10--15.
The registration for the Hinode 5 meeting is now open: http://hinode5.cfa.harvard.edu/Registration/.
July 1, 2011 is the deadline for early registration, abstract submission, and housing. Mark your calendars!
More information at the Hinode 5 website: http://hinode5.cfa.harvard.edu/.
Job Announcement: The Solar and Stellar X-ray Group at SAO is hiring for a Research Assistant position. Details on the job, qualifications and the application process can be found here: http://www.cfa.harvard.edu/hr/postings/11-40.html
Big News: Next week, Hinode-XRT operations will resume regular two-day timelines.
Big News: Due to interruptions in power at JAXA/ISAS and in Tokyo, we have had to simplify the Hinode-XRT operations for the short-term future. Single timelines will encompass several days of operations. As a consequence, Hinode-XRT planners will not be able to respond to rapidly changing conditions on the Sun during this period. However, on-board response functions (such as automatic exposure control and flare response tables) continue to operate nominally, and there is no impact to the safety of the instrument. We will keep you informed on this website as the operations conditions change.
Major Update: March 11 Letter from Hinode-XRT PI to Japanese Colleagues regarding earthquake and tsunami.
Dear Japanese Colleagues,
We are shocked and horrified at the damage that has been shown from the earthquake and tsunami. I am sure that many members of the Japanese solar community have been affected either directly or indirectly by the disaster. If there are actions that the US community can take to ease the burden during the coming weeks, please let us know. You are in our thoughts and prayers.
[March 11, 2011]
"Hinode Looks into a Hole on the Sun": An XRT image (Ti/poly) from Feb.1 is featured on the NASA/Missions/HINODE page this week. (The feature page is here.) UPDATE 2011-Feb-14: The feature is also being carried by Fox News now: "Scientists Discover Giant Holes in the Sun".
The paper "Quantitative Examination of a Large Sample of Supra-Arcade Downflows in Eruptive Solar Flares", by S.Savage and D.McKenzie, has recently been accepted for publication in The Astrophysical Journal. Expected publication is March 20, 2011, V730.
Recently, XRT took 9-filter synoptic observations on Jan 5 (12 UT), Jan 9 (20 UT), and Jan 13 (20 UT). We compared them with the corresponding images taken by SDO/AIA. The results can be found HERE.
XRT observed an annular eclipse on January 4, at approximately 9:16 UT. An image and a movie of the eclipse can be found on the XPOW page.
XRT operations have resumed using Filter Wheel 1 for high-cadence filter switching. This wheel contains thin filters (Al-poly and C-poly), as well as some of the thin/medium filters (Be-thin, Al-med, and Be-med). The latter are particularly useful for active region observations.
The paper "Temperature distribution of a non-flaring active region from simultaneous Hinode XRT and EIS observations", by Testa P., Reale F., Landi E., DeLuca, E.E., and Kashyap V., has recently been accepted for publication in The Astrophysical Journal. (Here's the link to the arXiv.org entry: http://arxiv.org/abs/1012.0346 .)
The paper "Coronal Temperature Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration", by N. Narukage, T. Sakao, R. Kano, H. Hara, M. Shimojo, T. Bando, F. Urayama, E. DeLuca, L. Golub, M. Weber, P. Grigis, J. Cirtain, and S. Tsuneta, has recently been accepted for publication in The Astrophysical Journal.
The paper "The Role of Magnetic Topology in the Heating of Active Region Coronal Loops," by J.-Y. Lee, Graham Barnes, K.D. Leka, Katharine Reeves, K. Korreck, L. Golub, and E.E. DeLuca, has recently been published in The Astrophysical Journal.
Big News! XRT-CO Sabrina Savage (MSU) successfully defended her PhD thesis!
Congratulations from the Hinode / XRT Team, Dr. Sabrina Savage!
2010-Oct-18 The Hinode Science Working Group (SWG) has announced that the Hinode-5 Science Meeting will be in Cambridge, Massachusetts, on October 11--14.
2010-Oct-18 XRT got nice observations of the M2.9 class flare at 19:02 UTC on 10/16, including pre-flare buffer images!
The XRT team has produced and released a substantial upgrade to the analysis software. This new release contains code that corrects for time dependent contamination of the XRT analysis filters and adjusts filter thicknesses to be consistent with the thorough analysis done by Narukage et al. (2010 Solar Physics, submitted). New tools for temperature and emission measure analysis are also included in this software release. Extensive documentation of these routines are contained in the program header information and descriptions of many of the XRT analysis tools are given in the XRT Analysis Guide (found at http://xrt.cfa.harvard.edu/resources/documents/XAG/XAG.pdf). All of the new software and associated data base files have been upload to the SolarSoftWare distributions site. Users of XRT data should be sure that their SSW IDL libraries are up to date.
Please send questions and report any bugs to xrt_manager [at] cfa.harvard.edu.
Note that the changes may take a day or two to percolate through SolarSoft.
XRT Project Scientist
2010-Sep-03 XRT image headers have a keyword, FLFLG, which indicates if the XRT flare flag has been set. The FLFLG keyword tells you if the XRT flare flag tripped but it does not tell you if XRT responded to the flare flag. As of reformatter version 1.52, beginning with images from about 2010/08/10 07:59, we have also added a new keyword, OBS_MODE, in order to indicate if XRT is running a flare mode program or a normal (quiet) mode program. This keyword is set to 'QT' if XRT is running a normal mode program and 'FL' if XRT is running in flare mode.
The OBS_MODE keyword does not exist in images processed before 2010/08/10, and the FLFLG keyword was not set correctly during a flare trigger in these prior images as well. We are working to update the XRT back catalog with correct information. In the meantime, the times when the XRT flare flag tripped, and information about whether or not XRT responded, can be found here: http://xrt.cfa.harvard.edu/missionops/flare_trigger_list/xrt_flare_flags.txt.
Please send any questions or concerns to xrt_manager_at_head.cfa.harvard.edu .
2010-Sep-03 The paper 'Multi-Stranded and Multi-Thermal Solar Coronal Loops: Evidence from Hinode X-Ray Telescope and EUV Imaging Spectrometer Data', by J.T. Schmelz, S.H. Saar, K. Nasraoui, V.L. Kashyap, M.A. Weber, E.E. DeLuca, and L. Golub, has been accepted for publication in The Astrophysical Journal.
2010-Aug-20 The XRT Team has just released a new upgrade to the basic XRT calibration
program xrt_prep.pro. (It should appear in the SSW tree in the next
few days.) The new version allows the user without a
local XRT data archive to setup automatic copying over the web of
darks required for the best (default) dark subtraction. The new
version also reduces error messages when files are not found, and
uses 512x2048 "strip darks" to approximate 2048x2048 darks in the
calibration for more recent 1x1 binned data (as 2048x2048 1x1 binned
darks are now rare due to telemetry issues). See the program headers
for more details.
Comments, feedback, and bug reports regarding these routines may be directed to this email address: xrt_manager_at_head.cfa.harvard.edu
2010-Aug-10 The paper 'Reconnection Outflows and Current Sheet Observed with Hinode/XRT in the 2008 April 9 "Cartwheel CME" Flare,' by S. Savage, D. McKenzie, K. Reeves, T. Forbes and D. Longcope has been accepted for publication in The Astrophysical Journal. A preprint can be found at on the arXiv preprint server at: http://arxiv.org/abs/1003.4758.
2010-July-26: A new X-Ray Picture of the Week is available! This movie shows AR11087 as it was observed coming around the East limb on July 09, 2010. This active region produced several C-class flares during its peak of activity from July 8-11th. It was also associated with CMEs observed by SOHO/LASCO on both July 8th and 9th. This movie shows one of the C-flares, pre and post-flare loop brightenings, as well as some hints of the ejected material that may have been observed by LASCO.
2010-July-11: XRT observed the July 11 2010 solar eclipse. This eclipse was visible from the South Pacific, and XRT/Hinode participated in joint observations with eclipse observers in The Cook Islands, French Polynesia, and Easter Island. A set XRT images from the eclipse can be found on the X-Ray Picture of the Week (XPOW) page.
2010-May-02: The 2010 Hinode/XRT team meeting will bring
together members of the Hinode teams and other scientific investigators
to discuss technical issues of XRT, scientific results, and plans
for future observations. The dates of the meeting are June 16
(Technical Discussion) and June 17-18 (Science Discussion), and the
location is Montana State University in Bozeman, Montana. The SOC
solicits your abstracts for this meeting. For additional information,
and the full announcement, please visit the meeting website at
2010-Mar-30: The calibration database for the CCD contamination layer has been updated; it is now current up to 2010-Feb-19. (This database is automatically accessed by the XRT SolarSoft code make_xrt_wave_resp.pro, which can be used to calculate the time-dependent effective areas.) Our intention is to update the database regularly after bake-outs. An improved analysis was used to recompute the layer thickness; users will note some changes in the computed thicknesses for data times before 2007-Sep-08.
2010-Jan-20: XRT observed the eclipse of Jan-15-2010. A movie of the moon eclipsing an active region can be found on the X-Ray Picture of the Day Page.
XRT is currently operating Filter Wheel 1 in "stepper mode". FW1 is currently set to the Al-med position. Early next week, FW1 will be moved to the Open position until further notice.
XRT observations have resumed at 2009-Nov-13, 0900 UT.
IMPORTANT--- XRT observations are expected to resume on the Saturday timeline (2009-Nov-14).
IMPORTANT--- XRT observations were halted on October 23, 2009, in order to perform some instrument tests. The date for resuming observations has not yet been set, and is pending the results of the testing.
The XRT CCD has experienced some degradation due to contamination that appeared after a short CCD bake-out in July. The contamination is manifest by small (~5 pixel diameter) spots on the detector. The spots cover somewhat less than 4% of the CCD area.They are seen in G-band images and in the thinner x-ray filters (Al_mesh, Al_poly, Ti_poly, C_poly and Be_thin, with decreasing effect in the order listed). The origin of the contamination is not understood at this time.
The XRT team is modifying the software in the SSWIDL tree to give scientists two ways of analyzing XRT data taken after the contamination event:
(1) a "touch-up" program that will replace the affected pixels with an average signal from near-by unaffected pixels.
(2) a "bad-pixel" map that allows scientists to avoid using the affected pixels in their analysis.
The touch-up program is applied to the quick-look images that are being distributed to web-pages and should be used when constructing movies and studying morphological changes. This same program will be available as a switch to the XRT_PREP code that converts level 0 data to level 1 data.
The XRT team is working to develop a cleaning program that will preserve the photometric information available below the spots. This programs will be distributed to the XRT user community through the SSWIDL distribution.
In addition the XRT team will develop programs that correct for the decrease in "filter-dependent" transmission between Nov-2006 and July-2007 caused by the accumulation of contaminants on the CCD. These corrections are particularly important for scientists using XRT data to estimate temperatures (e.g. via filter ratios).
The XRT team has setup an email distribution for users of XRT data. To subscribe to this list send an email to: firstname.lastname@example.org To reduce the amount of spam on this list, users are accepted by positive confirmation at SAO. Please include your signature file when requesting admission to this list. The XRT team will use the list to keep the community up-to-date on the latest analysis tools and developments. Users may use this list to ask questions about analysis, report bugs and discuss analysis techniques with other users. Email to this list will be archived at: xrt_users off the community page.