Important dates during the EIS mission#
Start of science operations (Nov 2006)#
The first science raster taken by EIS was on 23 Nov 2006 at 13:14 UT (the study "JTM004"). Prior to that, various test observations had been run, beginning on 27 Oct.
X-band antenna failure (Feb 2008)#
The failure of the X-band antenna is the single most significant event to affect EIS during the course of the mission. Problems first began towards the end of December 2007, with intermittent glitches for two months. The new era of S-band antenna observing began in February 2008. The transmission rate of the S-band antenna is 16 times lower than the X-band antenna, however additional downlink resources were secured .
During the X-band era, EIS would typically observe the entire day and the average date rate was typically 50 kbits/s. For the S-band era, daily data rates are typically about 6 kbits/s and a consequence is that EIS would generally not observe for 24 hours per day, instead focusing on shorter periods for which higher data rate studies could be run.
Less frequent planning (Mar 2008, Dec 2014)#
A consequence of the X-band failure is that Hinode planning switched from daily (Mon-Sat, with Sunday off) to three times a week (uploads on Tue, Thu & Sat) from about 20 March 2008 onwards. This impacted the ability to observe transient events, particularly flares.
In an effort to cut operations costs, "focused mode" operations began in December 2014. For these an entire 7-day plan is loaded on Saturdays. This only occurs during the Hinode and IRIS eclipse seasons (approx April-August and Oct-Feb, respectively), and only for selected weeks.
Grating mechanism adjustment (24 Aug 2008)#
An unusual effect in the early EIS data was a spatial offset in the X-direction between the SW and LW channels of 2 arcsec . This was mostly fixed with an adjustment of the grating position on 24 Aug 2008.
Regular spectral atlases (May 2010)#
EIS has a weekly synoptic program that takes full CCD spectral atlases on different solar features. Usually the study is Atlas_30, Atlas_60 or Atlas_120 (the number denotes duration in minutes). These did not begin until 17 May 2010, however, so atlases prior to this date are sporadic.
Pointing improvements (2014)#
For many years the EIS pointing was often not accurate, with the actual pointing being discrepant with the planned pointing by amounts of 5-30 arcsec. The worst examples were during the middle of the eclipse season (June-July) where the Y-offset could be up to 35 arcsec. With the launch of IRIS in 2013 efforts were made to improve this situation. An EIS-AIA alignment program was set up so that each day a large 40 arcsec slot raster was taken that could be co-aligned with AIA images. This allowed the team to be able to track the offsets with time, and demonstrated that the offsets vary in a regular pattern over the year. EIS planners from about 2014 onwards now make use of these offsets during planning and the actual pointings now agree very well with planned pointings (typically < 5 arcsec).
You can obtain accurate EIS coordinates prior to 2014 by following the method described in the EIS pointing section. The important point is that if EIS was coordinating with another instrument/observatory then there may be an unexpected offset in their relative positions as the EIS pointing offset wasn't accounted for during planning.
CCD bakeouts (2016 onwards)#
The EIS team avoided doing CCD bakeouts (which are common with EUV and X-ray instruments) due to concerns about whether they would affect the instrument calibration. However, bakeouts were finally performed in an effort to halt the continuous rise in the number of warm pixels on the EIS CCDs. The CCD manufacturer suggested a bakeout may reset the warm pixels.
Bakeouts were performed on 23-Feb-2016, 10-Aug-2017 and 17-Jan-2018. However, they did not have a significant impact on either the warm pixels or the calibration.
SOT filtergraph failure (Mar 2017)#
In March 2017 the SOT filtergraph failed and a consequence was that EIS and XRT were given increased data recorder allocations of 23% (up from 15%).
A brush with death (2018)#
EIS obtained no observations for over 4 months between January and May. The instrument shut down during a bakeout in January 2018, and the last raster began at 10:25 on 17 January. EIS was recovered, however, and science observations resumed with a raster at 07:39 on 25 May. No changes to the data quality were noticed after the recovery.