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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0230

SOT Observation of Mercury at Superior Conjunction

plan term


@ @


 name : Kameda, Katsukawa @  e-mail : yukio.katsukawa[at]nao.ac.jp

contact person in HINODE team

 name : Katsukawa @  e-mail : yukio.katsukawa[at]nao.ac.jp

 abstract of observational proposal
Mercury has thin atmosphere around the solid surface. Sodium (Na) is one of the abundant elements with strong emissions. There have been some observations reporting asymmetric distribution of the Na atmosphere between the dawn- and dusk-sides and between the high and low latitude regions, and its temporal variability of density distribution. The suggested source processes are photon-stimulated desorption by solar UV, solar wind ion sputtering, and micro-meteorite vaporization. It is suggested that interaction between solar wind and Mercuryfs magnetosphere causes the observed asymmetric distribution and temporal variation, however, even the dominant source process is still unclear. Hinode/SOT is only the instrument to get entire distribution of the atmosphere on the dayside with (1) spatial resolution enough to get latitudinal distribution of the Na atmosphere and (2) spectrum resolution to get emission of the Na line. The superior conjunction in May 2013 is a good opportunity to observe the dayside atmosphere of Mercury with Hinode/SOT because Mercury will lie exactly opposite to the Earth.

According to our estimation, we are able to catch signals from Mercury atmosphere by integrating more than ~1000 FG images with SOT. The images can be acquired if we run the observation with the highest temporal cadence for one hour during the passage of Mercury above the solar limb. The contrast of Mercury increases if we are able to capture emission of the Na D line from the Mercury atmosphere. This is why we run the wavelength scan with SOT/NFI to cover the expected emission wavelength.

 request to SOT
FG: NFI Na D Filtergram
- 5 wavelength points (-0.2A, -0.1A, 0A, +0.1A, +0.2A)
- 2Kx2K (160"x160") 4x4 sum (0.32" pixel)
- 80" ROI shift to observe above the limb
- Exposure time 0.5 sec (TBD)
- JPEG Q75 (TBD)
- Fastest cadence: 1.6sec/frame takes 8sec for one wavelength scan
 -> 2250 frames/hour
- Telemetry amount
 2250 x 512^2 x 1.5bit/pix = 0.8 Gbits

We will test the SOT program in advance to confirm suitable exposure time, JPEG compression, and telemetry amount.

 request to XRT

 request to EIS

 other participating instruments
MESSENGER (in-situ measurement)

[4] Time period of proposed observations, if required:
11 - 12 May 2013

[5] Time window in day, if required:
We will run the observation for one hour at both the ingress and the egress of Mercury (in total 2 hours).

Ingress: 2013/05/11 14:20-16:00
Egress:  2013/05/12 02:00-03:30

More precise information is to be provided later.

[6] Target of interest:
We will observe the west limb at the ingress and the east limb at the egress. The detailed pointing information is to be provided later.

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