The flight of the balloon-borne Sunrise observatory in 2009 demonstrated the high performance of the telescope and its post focus instrumentation in retrieving data with unprecedented resÊolution. The obtained data sets resulted in numerous publications (see, e.g., Astrophysical Journal Letters, Volume 723, Issue 2, Nov. 2010) and are still being analyzed by solar physics groups world-wide.
Already in 2009 we attempted to obtain co-observations with Hinode. Unfortunately, the problems with the direct communication link to Sunrise, resulting in the lack of knowledge of the exact pointing, made the coordinated observations almost impossible. Additionally, the lack of active regions on the solar surface did not allow for feature-oriented pointing information.
Although great efforts have been undertaken from the Hinode team, no dataset with a common field-of-view(FOV) could be recorded. This was a very unfortunate situation, especially since we know how much additional work the Hinode team put into the support of Sunrise, e.g. by changing tracking curves on Hinode on a daily basis.
With this experience in mind, we plan to change the observing strategy for the re-flight in 2013. The improved communication link between the ground station in Kiruna and the Sunrise observatory should allow for almost real-time control of the Sunrise pointing, and to obtain real-time thumbnail images of the observed region. Therefore, it should be rather straightforward to operate Sunrise as a slave instrument to Hinode.
The most promising strategy to obtain datasets of a common FOV is therefore to define Hinode as the master observatory. We ask the Hinode team to control the pointing in the usual manner by defining tracking curves for a two-day period in advance. These tracking curves are, as usual, displayed on the Hinode operations website, from where the Sunrise team can access the Hinode pointing for every given moment in time. Sunrise attempts to follow the Hinode coordinates. This strategy minimizes the efforts for the Hinode team in performing the co-observations and at the same time maximizes the chances of obtaining joint data sets.
The reflight of Sunrise in 2013 will concentrate on the observations of active regions. The scientific questions address all topics regarding the temporal evolution of the magnetic and velocity field in sunspot umbrae and penumbrae, the surrounding plage fields and pores at the highest achievable spatial resolution. New filters in the Sunrise Filtergraph (SuFi) will also allow to observe the chromosphere above these regions with unprecedented spatial resolution. These topics were already addressed in the scientific proposal for the Sunrise flight in2009 and could not be completed due to the lack of active regions in June 2009. The Sunrise science proposal for the reflight is currently under revision and will be made available for the co-observers as soon as possible.
The high spectral resolution of the SOT/SP telescope ideally complements the Sunrise data from the Imaging Magnetograph eXperiment (IMaX). IMaX will be operated in similar modes as during the 2009 flight, with some adjustments to allow for more sophisticated analysis techniques (i.e. height-dependent inversions applied to Stokes spectra sampled at 8 wavelength positions). In order to maximize the chances for overlapping FOV we propose to perform normal mode scans over active regions (as large as possible during the eclipse season, FOV ≈100~160arcsec2 ).
Albeit the FOV of the normal mode scans is smaller than of the fast mode scans, we prefer the normal mode scans. A newly developed, spatially coupled inversion technique applied to the Hinode SOT/SP data is optimized for the superior quality of the normal mode map data. Additionally, comparing the high spatial resolution data of Sunrise with Hinode data at the maximum possible resolution will simplify the analysis of the joint dataset.
The chromospheric capabilities of Sunrise have been extended by adding new filters to SuFi. The SuFi filters are:
1. The CaIIH filterfrom2009(396.80/0.18 nm),
2. a more narrow CaIIH filter (396.84/0.11 nm),
3. a 300/4.4 nm filter for the lower photosphere,
4. a Mg II filter (279.62/0.48),
5. 214/22 nm for the mid photosphere.
We ask to use a standard mode at highest possible spatial resolution (nobinning) for chromoÊspheric observations for Hinode NFI and BFI as the baseline for the co-observations.