Presentation by Dr. Ingo Richter - Max Planck Institute for Solar System Research (MPS)
Survey of the geomagnetic field and the electric field of the atmosphere
Absolute Scalar Magnetometer (ASM)
Vector Field Magnetometer (VFM)
("boom": extension or mechanical arm)
Investigates how the Sun's and Earth's magnetic fields connect and disconnect
key wave and very low frequency magnetic field measurements.
"The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS)" on this mission - link to dedicated section on instrumentation:
"Magnetic field measurements in space" - Instrumentation starting at third page
"Magnetograms are often produced by exploiting the Zeeman effect (or, in some cases, the Hanle effect)".
"Soon after George Ellery Hale discovered a way to detect magnetism on the sun in 1908, large telescopes were created to make more detailed observations using the Zeeman Splitting Effect.
One of the largest of these telescopes, the Mt. Wilson 150-foot tower telescope, was built in 1912.
The NASA-Marshall Space Flight Center Vector Magnetograph Facility was assembled in 1973 to support the Skylab mission. At this facility, daily magnetograms can be accessed online since 2000.
Meanwhile in space, the NASA/ESA SOHO satellite creates magnetograms of the full sun (...)".
Solar and Heliospheric Observatory (SOHO)
SOHO carries the Michelson Doppler Imager (MDI) which measures velocity and magnetic fields in the photosphere.
Magnetometry with LGS technology
In a previous section, we referred to the "Laser Guide Stars". The publication by W. Happer et al (https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-11-1-263) is considered to be a major reference. W. Happer, a physicist who pioneered spin-polarized spectroscopy and the sodium Laser Guide Stars, had thought of using LGS for Magnetometry but never published on the subject. Below, preceded by a commentary, is the first publication on the subject by a team consisting of members of D. Budker's lab and also scientists of ESO.
"Physicists propose beaming laser at atmospheric sodium to measure global magnetic field"
What is the magnetometric sensitivity of the technique?
"The calculated magnetometric sensitivity, which is limited by currently available laser power and may therefore be expected to improve with advances in laser technology, is useful for the envisaged geophysical applications which require measurement of fields, e.g., in the 1–10 nT range for ocean circulation  and the tens of nanotesla range for the solar-quiet dynamo ; moreover, the dynamic range of the measurement is not subject to any simple physical limit, as the resonance technique works well and with similar sensitivity at any magnetic-field strength. Moreover, the sensitivity of this technique could be further enhanced by as much as five orders of magnitude by reflecting a laser from a rocket- or satellite-borne retroreflector, instead of being limited to the small fraction of fluorescence emitted toward the detecting telescope."
10 to the minus 9 enhanced by 5 orders of magnitude is 10 to the minus 14, one order below the femtotesla.
Please note that the brain magnetic field is in the order of picotesla and femtotesla (cf.
Figure 2: Facebook post from Laser Focus World
"Researchers at the Shanghai Institute of Optics and Find Mechanics (SIOM) have succeeded in developing a high-power 589 nm sodium laser pulsed at the Larmor frequency in the 200–350 kHz range for remote magnetometry, which translates to analysis of 100-km-scale variations at the ground: https://goo.gl/X4miT4"
Cited study at https://www.ncbi.nlm.nih.gov/pubmed/?term=29088161
Environmental magnetometric capabilities using light (lasers) are reported to have increased by an order of magnitude in 6 months.
Sensitivity reported to be at 28 nT/Hz½ (noise-equivalent power)