NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Magnetometer (Mag)

NSSDCA ID: 2007-043A-04

Mission Name: Dawn
Principal Investigator:Dr. Christopher T. Russell


The Dawn magnetometer is designed to measure low-level magnetic fields due to the asteroids and the effects of the asteroids on the solar wind magnetic field. The primary scientific objectives are to determine if the asteroids possess natural remnant magnetization and, through geologic correlations, when it was produced and to measure transient magnetic fields and how they are affected by the asteroids, providing constraints on the electrical conductivity of the interior. The magnetometer measures magnetic fields in the range -1000 to +1000 nT at 20 Hz at a resolution of 0.015 nT.

The magnetometer is a fluxgate type using dual ring-core sensors mounted on a 5 meter boom. One sensor is mounted at the end of the boom and one is mounted 1/3 of the way down to provide an estimate of spacecraft magnetic fields. The spacecraft itself, including the ion drive, has been designed to minimize the effect at the magnetometers, which is estimated to be at the 10 nT level. An electronics unit drives the ring-core sensors at 12 KHz. The amount of second harmonic signal in quadrature with the drive frequency is detected and nulled by a feedback circuit. The current required to keep the ring-core at zero field is a measure of the strength of the external field. The main electronics board contains a power supply, drive, sense and feedback circuitry, and digital command and control circuitry. The instrument is calibrated via an internal calibration source. The mass of the electronics unit is 2.35 kg and of the sensors and cable 0.7 kg. The instrument baseline is maintained at better than 0.1 nT and the time varying field is measured to 3E-5 nT squared per Hz at 1 Hz.

Alternate Names

  • Dawn/Mag
  • Mag

Facts in Brief

Mass: 3.05 kg
Power (avg): 3 W


  • Planetary Science: Small Bodies
  • Planetary Science: Fields and Particles

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Christopher T. RussellPrincipal InvestigatorUniversity of California, Los
[] NASA Logo -