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The Helioseismic & Magnetic Imager on the Solar Dynamics Observatory. The HMI Team – Stanford University, LMSAL, HAO, ++. HMI Data Processing. Data Product. HMI Data. Internal rotation Ω(r,Θ) (0<r<R). Spherical Harmonic Time series To l =1000. Heliographic Doppler velocity maps.

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TheHelioseismic & Magnetic Imageron theSolar Dynamics Observatory

The HMI Team – Stanford University, LMSAL, HAO, ++

HMI Data Processing

Data Product

HMI Data

Internal rotation Ω(r,Θ)




Time series

To l=1000


Doppler velocity



Mode frequencies

And splitting

Internal sound speed,

cs(r,Θ) (0<r<R)

Full-disk velocity, v(r,Θ,Φ),

And sound speed, cs(r,Θ,Φ),

Maps (0-30Mm)

Local wave

frequency shifts

Ring diagrams




Carrington synoptic v and cs

maps (0-30Mm)




Tracked Tiles

Of Dopplergrams

Wave travel times

High-resolution v and cs

maps (0-30Mm)

HMI Major Science Objectives

Egression and

Ingression maps

Wave phase

shift maps

Deep-focus v and cs

maps (0-200Mm)


  • The primary goal of the Helioseismic and Magnetic Imager (HMI) investigation is to study the origin of solar variability and to characterize and understand the Sun’s interior and the various components of magnetic activity. The HMI investigation is based on measurements obtained with the HMI instrument as part of the Solar Dynamics Observatory (SDO) mission. HMI makes measurements of the motion of the solar photosphere to study solar oscillations and measurements of the polarization in a spectral line to study all three components of the photospheric magnetic field. HMI produces data to determine the interior sources and mechanisms of solar variability and how the physical processes inside the Sun are related to surface magnetic field and activity. It also produces data to enable estimates of the coronal magnetic field for studies of variability in the extended solar atmosphere. HMI observations will enable establishing the relationships between the internal dynamics and magnetic activity in order to understand solar variability and its effects, leading to reliable predictive capability, one of the key elements of the Living With a Star (LWS) program.

  • The broad goals described above will be addressed in a coordinated investigation in a number of parallel studies. These segments of the HMI investigation are to observe and understand these interlinked processes:

  • Convection-zone dynamics and the solar dynamo;

  • Origin and evolution of sunspots, active regions and complexes of activity;

  • Sources and drivers of solar activity and disturbances;

  • Links between the internal processes and dynamics of the corona & heliosphere;

  • Precursors of solar disturbances for space-weather forecasts.

  • These goals address long-standing problems that can be studied by a number of immediate tasks. The approaches to study these processes reflect our current level of understanding and will obviously evolve in the course of the investigation.

Far-side activity index






Magnetic Field Maps



Full-disk 10-min

Averaged maps

Vector Magnetograms

Fast algorithm

Vector Magnetic

Field Maps

Vector Magnetograms

Inversion algorithm

Coronal magnetic

Field Extrapolations

Tracked Tiles

Tracked full-disk

1-hour averaged

Continuum maps

Coronal and

Solar wind models



Solar limb parameters

Brightness Images

Brightness feature


HMI Data Analysis Pipeline

HMI/AIA JSOC(Joint Science & Operations Center)

HMI Implementation

The HMI instrument design and observing strategy are based on the highly successful MDI instrument, with several important improvements. HMI observes the full solar disk in the Fe I absorption line at 6173Å with a resolution of 1 arc-second. HMI consists of a refracting telescope, a polarization selector, an image stabilization system, a narrow band tunable filter and two 4096² pixel CCD cameras with mechanical shutters and control electronics. The continuous data rate is 55Mbits/s.

The polarization selector, a set of rotating waveplates, enables measurement of Stokes I, Q, U and V with high polarimetric efficiency. The tunable filter, a Lyot filter with one tunable element and two tunable Michelson interferometers, has a tuning range of 600 mÅ and a FWHM filter profile of 76 mÅ.

Images are made in a sequence of tuning and polarizations at a 4-second cadence for each camera. One camera is dedicated to a 45s Doppler and line-of-sight field sequence while the other to a 90s vector field sequence. All of the images are downlinked for processing at the HMI/AIA Joint Science Operations Center at Stanford University.

  • Data Capture from SDO ground system

  • Archive of telemetry and processed data

  • Distribution to team and exports to all users

  • HMI and AIA processing to “level-1”

  • HMI higher level science data products

Fold Mirror Assembly

BDS Beam-splitter Assembly

Michelson Interferometer

Alignment Mechanism

Filter Oven Assembly

Lyot Filter Assembly

Oven Controller E-Box

Focus Mechanism

ISS Mirror Assembly

Hollow Core Motors

Secondary Lens Assembly


Focal Plane Assembly

ISS Beam-splitter Assembly

Limb Sensor Assembly

ISS Pre-Amp Electronics Box

Camera Electronics Box

Telescope Assembly

Primary Lens Assembly

Front Window Assembly

Front Door Assembly

  • Expect to archive ~ 1000TB/yr

  • Metadata stored in PostgreSQL database

  • Image data is stored online and on tape (LTO-4)

  • “Pipeline” processing system to generate standard products

  • Special products computed automatically “on demand”

HMI Principal Optics Package Components

Mechanical Characteristics:

Box: 0.84 × 0.55 × 0.16 m

Over All: 1.19 × 0.83 × 0.30 m

Mass: 44.0 kg

First Mode: 73 Hz


Optical Characteristics:

Effective Focal Length: 495 cm

Telescope Clear Aperture: 14 cm

The solid lines show the HMI filter transmission profiles at 76 mÅ spacing. The black dashed line is the profile used for the continuum filtergram. The dotted line shows the Fe I line profile.



HMI – AIA Joint Science Operations (JSOC-SDP)

Science Data Processingfor theSolar Dynamics Observatory

The JSOC-SDP Team – Stanford University

  • HMI Recent Progress & Current HMI Activities

  • (as of May 2010)

  • SDO with HMI was launched on Feb 11, 2010.

  • The HMI aperture door was opened on March 24.

  • The SDO commissioning was complete on April 30.

  • Regular observations with preliminary calibrations are available since

  • May 4 for data from door opening to the current day – 1.

  • Calibration and “observable” analysis code development

  • activities are continuing.

  • We expect stable data products to be regularly available starting mid

  • June 2010.

  • HMI “level-1” science data will be available within a day or so after

  • observation.

  • Regular processing of higher level products will begin during the

  • next few months.

  • There will be about 5 months of overlap with SOHO/MDI for

  • cross-calibrations.

  • Access to HMI data is available via the HMI/AIA JSOC (see right half

  • of this poster) and VSO.

The JSOC consists of three components: The IOC (Instrument Operations Center) at LMSAL performs instrument operations for both HMI and AIA; The SDP (Science Data Processing) facility at Stanford handles data for both HMI and AIA by receiving it from the SDO ground system, short term and long term archive, processing to “level-1” products for both instruments, higher level processing for HMI and data access and export for both instruments; The AVC (AIA Visualization Center) provides tools for interactive inspection and analysis of AIA images and HMI magnetic data.

Products from Level-1 and above are served through the open server at the JSOC web site. The higher level products are in development and are expected to become available over the coming months.

  • The JSOC web site includes a “wiki” for JSOC documentation, online code documents are maintained by the Doxygen system, the base infrastructrue code is maintained in the CVS system with online access. Basic tools (AJAX style) are available for inspection of image metadata and access to individual data files. Data is maintained in compressed FITS files with minimal headers. The data metadata is maintained in a PostGreSQL database. Metadata may be bound to data files on export. The metadata system and supporting software API is called the “Data Record Management System” (DRMS). The basic unit of storage is called a “Storage Unit” and maintained by SUMS (Storage Unit Management System). The DRMS/SUMS system has heritage in the SOHO/MDI data system. DRMS/SUMS make each of the expected many hundreds of millions of files individually available. SOHO/MDI data has been ingested into the JSOC DRMS/SUMS system as its Resident Archive and had been the source of most exported MDI data for several years.

  • SDO (HMI and AIA) is available through multiple channels:

  • Direct access via programming interface in “c” for pipeline processing and local analysis.

  • Basic access and export directly from the JSOC data servers,

  • High volume users are served by the netDRMS distributed data system.

  • Most Level-1 and selected higher level products via the Virtual Solar Observatory (VSO),

  • 3rd party servers such as will provide streaming access to images.

  • JSOC-AVC will provide daily images to science museums and planetariums.

  • The AVC will provide a “Sun Today” web service.

  • NASA SDO will provide high volume access for selected event image sequences.

HMI Data Products and Access

All HMI data is available. Science level data products are being placed on an open web server with a lag of a day or so of time of observation.

Lower level and intermediate products are available on request.

The data volume is large, more than a terabyte per day. Thus we encourage users to export only the data they actually need for immediate analysis. We are committed to provide tools to allow subsetting of the data and of providing multiple access tools appropriate for different data volumes for different users.

Contributors to the HMI development up through launch include: