The Plasma-Mag instruments are intended to measure the magnetic field and the velocity distribution functions of the electron, proton, and alpha components of the solar wind (Faraday cup) at high time resolution. A much-improved time resolution is possible because Triana is a 3-axis stabilized spacecraft permitting near-continuous measurements at several times per second. Previous solar-wind measurements from the spin-stabilized WIND spacecraft could only be made when the Faraday cup pointed towards the Sun. The system to be used to reduce and interpret the data from the Plasma-Mag instruments is derived from the algorithms in use for WIND, which have been shown durable and well suited for scientific work.
Plasma-Mag contains a triaxal fluxgate magnetometer that will investigate solar- wind magnetic fields with a sensitivity level of better than 0.1 nT. The present design has been optimized for small size, low power, simplicity, and a very large dynamic range. Using the latest technology, it achieves a dynamic range of almost 8 orders of magnitude in field measurement capability simplifying its implementation aboard the Triana spacecraft.
The tophat electrostatic analyzer will make measurements of the electron between 3 EV and 2 KEV. The 3D measurement will be accomplished by electronically simulating the data sampling of an electron spectrometer on a spinning spacecraft. The instrument has a set of anodes distributed uniformly in azimuth, each with a field of view 50° x 7° in azimuth and elevation.
In addition to Sun and solar-wind studies, the data will also be used to provide early warning of solar events that might cause damage to power generation, communications, and other satellites (see Figure 32 for an example of Plasma-Mag measurements). Together, the Plasma-Mag suite of instruments will provide a 1-hour warning to the appropriate agencies that safeguard electrical equipment on Earth and satellites in Earth orbit. Present plans include routinely giving the data to NOAA with only a 5-minute data processing delay from detection of an event at the Triana spacecraft position to the time that it is delivered.
The data shown in Figure 32 are obtained with WIND instruments that are similar to those carried onboard Triana. The similarity allows the algorithms and analysis techniques to be adapted to the new instruments with a great degree of certainty for success. Triana instruments are an improvement over those used previously, especially because of the 3-axis stabilized spacecraft. Because of this, the frequency of measurements will be much higher, allowing the scale in Figure 32 to be minutes instead of days. The high-time resolution of the measurements is necessary for revealing the wave structure of charged particles streaming past the Triana spacecraft. Triana, combined with other spacecraft already at L-1, will allow the detection and analysis of large-scale magnetic and plasma structures.
Because of the growth of satellite communications for civilian and military purposes, monitoring of the solar weather has become a mandatory function of government. Plasma-Mag will add to, or replace, the first generation space-weather monitors, such as WIND, IMP-8, and ACE. For example, ACE, the most recently launched, is concentrated upon solar wind isotopic composition, rather than particulars of the solar wind flow. Thus, Plasma-Mag provides an essential augmentation of present solar wind observations.
