Le ST5 KuaFu Symposium 2007 01

Space Technology 5 Measurements of Field-aligned Currents: Initial Results: 

Space Technology 5 Measurements of Field-aligned Currents: Initial Results Guan Le NASA Goddard Space Flight Center In collaboration with J. Slavin, R. Strangeway, Y.-L. Wang, and S. Boardsen

ST5 Mission Overview: 

ST5 Mission Overview NASA New Millennium Program mission to flight-validate new concepts and technologies Designed, built and operated three 25 kg spacecraft utilizing breakthrough technologies Demonstrated the ability to achieve accurate, research-quality scientific measurements utilizing a constellation of 3 micro-satellites Operated the three satellites as a single Constellation “Pathfinder” for future missions of 10’s or 100’s of small spacecraft

ST5 Mission and Orbit Profile: 

ST5 Mission and Orbit Profile 224 094 155

ST5 Miniature Fluxgate Magnetometer: 

ST5 Miniature Fluxgate Magnetometer Research quality tri-axial fluxgate magnetometer Two dynamic ranges: 0 - ±64,000 nT (Full-field) 0 - ±16,000 nT (Low-field) Digital Resolutions: better than1.3 nT (Full-field) better than 0.3 nT (Low-field) Sample Rate: 16 samples/s Provider: UCLA

Slide5: 

Field-Aligned Currents: Separating Space and Time Spatial Variation Temporal Variation

Slide6: 

ST5 Trajectories on April 14, 2006

Slide7: 

ST5 Trajectories on April 14, 2006

Slide8: 

ST5 Observations of Field-Aligned Currents (2006-04-14)

Slide9: 

Field-Aligned Currents Motion, Thickness, and Density (2006-04-14) Motion of Current Sheets - S/C speed in initial frame: 6.45 km/s - FAC speed in Initial frame: 0.66 km/s - FAC speed in S/C frame: 5.79 km/s Current Sheet Thickness (from SC094) - Downward FAC (flowing into the ionosphere): 306 km - Upward FAC (flowing out of the ionosphere): 1447 km If using data from single spacecraft - 10% overestimate in current sheet thickness - 10% underestimate in current density

ST5 Gradiometer Measurement of FAC Intensity: 

ST5 Gradiometer Measurement of FAC Intensity

Field-Aligned Current Speed Relative to Vsc: 

Field-Aligned Current Speed Relative to Vsc

Slide12: 

ST5 Field-aligned Currents – Polar Auroral Image ST 5 measures field-aligned current flowing into/out of auroral arcs imaged by Polar VIS Camera (N2+ UV band)

ST5 Science Validation - Initial Results: 

ST5 Science Validation - Initial Results ST 5 micro-satellites provided excellent support for science measurements: Highly stable spacecraft - no measurable nutation or coning; Magnetically clean spacecraft - no measurable stray s/c stray fields; Precision sun-sensor achieved ± 0.1º pointing knowledge. First micro-satellite constellation magnetic field measurements in LEO: First unambiguous separation of FAC temporal and spatial variations using two point magnetic field measurements on time scales of 7 - 700 sec and 50 - 5500 km; First measurements of FAC intensity using two point magnetic field gradiometry.

ST5 Launch Animation: 

ST5 Launch Animation

Backup Charts: 

Backup Charts

ST5 Observations of ULF Waves in Pc2 Band (~ 0.1 Hz): 

ST5 Observations of ULF Waves in Pc2 Band (~ 0.1 Hz)

ST5 Observations of ULF Waves - Hi-pass Filtered Wave Data: 

ST5 Observations of ULF Waves - Hi-pass Filtered Wave Data

ST5 Observations of ULF Waves - S/C Magnetic Footprints : 

ST5 Observations of ULF Waves - S/C Magnetic Footprints

Slide19: 

Green: ST 5 Two Spacecraft Gradient Measurement Red: Comprehensive model (CM4) Model Prediction 2006 Day 091 Start UT: 0200 ST 5 Science Validation – Crustal Magnetic Fields

Slide20: 

The higher frequency content of the ST-5 gradient observations allows a higher resolution view of the Gulf of California spreading center. Direct Measurement of Crustal Magnetic Field Gradients

ST-5 Science Validation - Initial Results: 

ST-5 Science Validation - Initial Results ST 5 micro-satellites provided excellent support for science measurements: Highly stable spacecraft - no measurable nutation or coning; Magnetically clean spacecraft - no measurable stray s/c stray fields; Precision sun-sensor achieved + 0.1º pointing knowledge; Position knowledge typically < + 1 km. First micro-satellite constellation magnetic field measurements in LEO: First unambiguous separation of FAC temporal and spatial variations using two point magnetic field measurements on time scales of 7 - 700 sec and 50 - 5500 km; First measurements of FAC intensity using two point magnetic field gradiometry; First crustal anomaly measurements using two point magnetic field gradiometry.