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Data Problem
John Davis
29 Feb 2008
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The Hinode Solar Observatory is currently experiencing technical difficulties that have resulted in a reduction in the rate at which scientific data can be transmitted to the ground from the on-board recorder. This is a purely spacecraft transmission problem and has not affected the quality or the short term cadence of the scientific data that is being recorded on-board by the three instruments. The cause of the problem has been limited to two possible areas in the data transmission system. Both are under investigation, but no clear conclusion has yet been reached or remedial action identified and unfortunately none is expected in the near term.
The Hinode team is developing procedures to minimize the impact of this problem including greater data compression, adding additional ground stations and implementing an alternate data transmission scheme. The team is also developing observational programs streamlined for scientific efficiency and comprehensiveness. Nevertheless the problem will have a significant impact on the way the mission is operated. One of the near term impacts is the ability to accommodate observations by non-team members through the HOP (Hinode Operation Plan) process. Consequently we have imposed a one month moratorium on all HOPs that will extend through March 31, 2008. Although observing proposals are still encouraged, they will undergo greater scrutiny before approval than has been the case up to now. Scientists wishing to propose HOPs should plan for smaller data volumes than those previously allowed. Although larger data sets can be accommodated, strong scientific justification will be required for them to be accepted into the planning process. If a proposal is accepted the Scientific Schedule Coordinators will assign a team member to assist in scaling the observations to acceptable levels.
It is difficult to place a time on when a return to normal operations may be expected but it appears that this is a long rather than a short term problem. In the meantime high quality Hinode observations are continuing to be obtained by all three instruments, SOT, XRT, and EIS. We hope that you will continue to use the Hinode data in your research and bear with us while we work to resolve this problem.
A technical review of the anomaly is being prepared by JAXA and will be available shortly. (Hinode is a joint JAXA/NASA/UK/ESA mission.)
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Data Availability
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All data obtained with Hinode is available through the
Data Archives and Transmission System (DARTS) at the Hinode Data Center in Japan and at the Hinode Science Data Centre Europe. Also see the
Virtual Solar Observatory (at the moment, XRT data only). For SOT and XRT data, see Lockheed-Martin and for the EIS archive, see Mullard Space Sciences Laboratory. For more information on data usage and analysis, see the following:
XRT Analysis After CCD Bake-out in July
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:
- a "touch-up" program that will replace the affected pixels
with an average signal from near-by unaffected pixels.
- 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 program 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:
xrt_users-request@head.cfa.harvard.edu
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:
http://xrt.cfa.harvard.edu/community/xrt_users
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Data Policy
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The Hinode Team agreed to the following approach to the release of the scientific data from the three instruments. The
policy is as follows:
The international members of the Hinode team have adopted the following approach to the release of the data from the
three Hinode instruments.
- The observations recorded during the first six months of operations, which includes the commissioning
phase and initial operations, will not be released on time. As a result of various difficulties in commissioning, calibrating the instruments, and creating analysis software, the Hinode team made the decision to release the data in May at the Solar Physics Division meeting (May 27-31) in Hawaii. It is anticipated that until then,
limited blocks of data will be released to provide the wider scientific
community with an opportunity to interface with the database and to provide feedback to the Hinode team prior to the full
release of data.
- After the first six months all observations will be made available to the scientific community as soon as
they are received and processed at ISAS.
Japanese students, who have operational responsibilities, will be provided limited protection for the data that are
assigned to use for their PhD thesis topic. This does not restrict the use of the data by other scientists but relies on
the user (Gentlemen's Agreement) to check with either the student or his advisor to ensure that their use of the data does
not directly conflict with the student's work. It is hoped that a side benefit of this process is that it will create
contacts between the student and other scientists interested in similar topics.
This policy was approved by the Hinode Science Working Group on November 12, 2005.
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