JOP226 SOHO-SDO Cross-Calibration

Authors:
Phil Scherrer, Rock Bush, Sarah Gregory

Participating Instruments:
SDO/HMI
SOHO/MDI


Scientific Objective & Justification:
SOHO/MDI has operated nearly continuously for more than 14 years 
collecting a unique and important set of solar observations.  The long time 
span allows many studies of the 11/22 year solar cycle with direct well 
calibrated observations.

The MDI instrument will be turned off several months after the launch of SDO.
The Helioseismic and Magnetic Imager instrument on SDO will continue MDI-type
observations during the SDO mission.  HMI has significant design heritage from 
MDI but it is not identical and the differences will be revealed in detailed 
comparisons of simultaneous observations.  The goal for SDO is to continue for 
up to 10-years (base mission is 5 years).  If we are Merging MDI and HMI observations
(reduced to MDI resolution) provide a very beneficial 20-25 year span - a full solar 
magnetic cycle - of intercomparable data.  Sufficient overlap data  will allow a
20+ year span rather than two half-magnetic-cycles from two instruments with
different responses.  

Operational Considerations:
The SDO/SOHO Cross-calbration requires continuous DSN support for 60 days (04 May 2010 through
11 July 2010) to obtain continuous MDI Structure and Campaign data as well as 96 minute Synoptic 
MDI Magnetogram data.

The guidelines for SOHO Continuous Contact operational procedures is outlined in a standing SOHO 
OCD titled "Standard MDI Operations Policy".

The Cross-calibration will further require enough DSN support to allow for continuous Structure 
data and downlink of daily synoptic high rate Magnetograms during and after the August 2010 SOHO Keyhole.
An August 2010 Keyhole OCD and a new Standard Operations Policy will be drafted to explain new 
requirements for SOHO operations concerning MDI data downlink modes during these periods.  

Detailed Observing Sequences:
MDI:
     Start with three days of high resolution FOV Doppler, magnetogram
     and filtergram at disk center.
     cam_hr_t_ve_fe_me: HR velocity, HR filtergram and HR mag 500x1024

     Followed with thirty days of full disk Doppler and high resolution
     FOV Doppler at disk center.
     cam_p30v_hr_ve: FD P30 velocity (R=504) and HR 1024x600 velocity

     Calibration sequence run in transition after thirty days of full
     disk/high res Doppler.

     Remainder of Dynamics with full disk Doppler and selected second
     observable. Observing duration of 3 to 4 days suggested for each
     of the following:
     cam_p30v_hr_me:  FD P30 velocity (R=504) and HR 1024x640 magnetogram
     cam_p30v_hr_le:  FD P30 velocity (R=504) and HR 1024x640 linedepth
     cam_fd_v1_l1:    FD velocity (R=504) and FD linedepth (R=504)
     cam_p30vr_fd_m1: FD velocity (R=480) and FD magnetogram (R=504)

     If an active region is in the MDI high resolution FOV, switch to a
     high resolution FOV Doppler, magnetogram and filtergram observing
     program:
     cam_hr_ve_fe_me:    HR velocity, HR filtergram and HR mag 1024x500
     cam_hr_t2_ve_fe_me: HR velocity, HR filtergram and HR mag 700x700

     With an active region at central meridian and in the MDI high res FOV,
     several hours of high resolution magnetic line scans should be taken
     on the active region.
     cam_hr_mag_lp_e256:  Line profile for HR magnetogram frames (256 extract)
     cam_hr_mag2_lp_e256: Line profile for HR magnetogram frames (256 extract)

     If a "good" active region is outside the MDI high resolution FOV,
     several hours of full disk magnetic line scans should be run.
     cam_fd_mag_lp_e256:  Line profile for FD magnetogram frames (256 extract)
     cam_fd_mag2_lp_e256: Line profile for FD magnetogram frames (256 extract)