Title: 
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GOLF-VIRGO-MDI  Intercalibration

Lead Investigator:
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B. Andersen (VIRGO), T. Hoeksema (MDI), R. Ulrich (GOLF)

Team Members:
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T. Appourchaux, R. Bogart, C. Wehrli, Boumier, Henney +++		     

Local Coordinator:
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T. Hoeksema

Lead Programmer:
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Technical Summary:
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Investigate the noise properties of the data products of the 
respective instruments by detailed intercomparisons. To achieve 
the scientific objectives of the individual investigations and 
the SOHO mission as a whole it is essential that the level, the 
spatial and time variation of both the instrumental and solar 
noise is understood.

The goal of this proposal is in the first instance not scientific,
but rather to provide tools do to better science with the SOHO
seismology instruments. 
 
        

Proposal Text:
=======================
The specific outputs of this study will be:




The results of this study will be provided to all the investigators 
of the GOLF, MDI and VIRGO investigations to aid them in the 
scientific interpretation of the data.

This study will be based on a short (	 2 weeks) simultaneous time 
series from the three participating instruments. The length of 
2 weeks is required to follow structures rotating over the solar 
disc. To be able to aid the other investigations this time series 
should be taken as early as possible in the cruise phase. 
In addition attempts will be made to coordinate small snapshots 
of high resolution and other ground based observations.
T

The study requires the following data obtained simultaineously 
from the SOHO helioseismic instruments:

VIRGO SPM 			(Level-1+)
VIRGO LOI			(Level-1+)
GOLF				(Level-1)
MDI LOI Proxy		(Level-1)
MDI FD Velocity		(Level-0.5/1)
MDI B, Ic, Il

In addition shorter units of the following ground based data is 
wanted:
Mt. Wilson Doppler/Magnetograms
GONG Velocity, Ic, Il
La Palma I, V and B high resolution data for 1-3 hours at 3 
heliocentric positions (cos(theta)=1.0, 0.5, 0.2).

Furthermore the output from the SOHO coronal instruments should 
be monitored for extradordinary activity (strong flares etc.) 
that may influence the signals.

The available timeseries at different spatial resolutions will be
 compared by successively deterioating the spatial resolution. 
For intensity measurements this could be the sequences:
1.	La Palma (short snapshot)
2.	MDI Ic,, full resolution (8hours)
3.	MDI Ic,, GONG resolution (24 hours)
4.	GONG Ic,, full resolution (24 hours)
5.	MDI Ic,, LOI proxy subset resolution (2 weeks)
6.	MDI Ic,, LOI proxy resolution (2 weeks)
7.	LOI single pixel resolution (2 weeks)
8.	LOI added pixels (2-12) resolution(2 weeks)
9.	SPM (2 weeks)

Similar types of sequences apply to the velocity measurements. 
There has to be close interaction between the interpretation of 
the velocity and intensity intercomparisons to understand the 
effects of velocity/intensity cross-talk in the MDI data.

As the final part of the work comparisons of the noise signatures 
in velocity and intensity should be carried out.

Responsibilities
Each of the main investigators has the responsibility of making 
the required time series from the respective instruments available
 to the other investigations.

The interface to the required ground based data has not been 
identified.



See Also:
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