Solar Probe Plus
Solar Probe ( also Solar Probe Plus) is a planned spacecraft NASA to study the Sun, especially its outermost layer of the atmosphere, the corona. You should answer two unresolved issues:
For this purpose, Solar Probe will approach to the sun's surface at 8.5 solar radii. Solar Probe is intended to replace the cost reasons Painted in the concept stage Solar Probe, which should approach the Sun's surface to within three radii. According to current plans, the launch of the spacecraft is scheduled for July 30, 2018, after seven swing - bys of Venus they should at December 19, 2024 reached its point nearest the Sun for the first time.
History
The idea of a space probe to study the Sun from an extremely close range, was mentioned for the first time in October 1958 in a study by the National Academy of Sciences. Since the high temperatures were not controlled in the vicinity of the Sun, but only studies have been made for decades.
Original Mission Solar Probe
According to the original mission planning Solar Probe of an Atlas V should be 551 started with an additional Star 48 upper stage to Jupiter and from him by a swing-by maneuver in a highly elliptical, 90 ° inclined, polar solar orbit will be redirected to the ecliptic, the perihelion should only three solar radii above the solar surface. In order to withstand the extreme heat in three solar radii above the solar surface, a spitzkegeliger towards the sun sun protection was provided, which was shown glowing in some pictures from heat. Behind this 2.7 m wide sun protection ( in its shadow ), the actual probe body would have been, and only the tips of the plasma antennas have hinausgeragt from his shadow cone. Since the flyby of Jupiter and because of the high temperatures in extreme perihelion no solar cells can be used, Solar Probe should the necessary electrical energy from three multi-mission Radioactive Thermoelectric Generator ( MMRTGs, see: radionuclide ) gain, which are mounted directly below the sun shield should. During the approximately nine-year mission, the Solar Probe twice the perihelion of four solar radii above the center of the Sun at a speed of 308 km / s pass and the sun should be coming from the south, flying over. The take-off mass of the Solar Probe should be about 856 kg. Because of MMRTGs the concept proved too expensive for NASA.
Solar Probe
Because of the important issues of the mission, NASA gave the Applied Physics Laboratory (APL ) of the Johns Hopkins University ( JHU ), it was to build the Solar Probe, a second study in order to be without RTGs this time.
Solar Probe will be launched by an Atlas V 551 with an additional Star - 48BV upper stage to Venus, where it performs the first swing-by maneuver. Three months after the start they achieved in the first perihelion, with 35 solar radii from the Sun's center. By further swing-by maneuver at Venus gives off Solar Probe more orbital energy of Venus, causing the perihelion every time is closer to the Sun's surface. After the seventh swing-by, Solar Probe approaches the solar surface up to 8.5 solar radii (about 5.91345 million km ) at perihelion. The heliocentric velocity of the probe then reaches 200 km / s This final orbit has an aphelion of 0.73 AU at 3.4 ° inclination to the ecliptic, and an orbital period of 88 days. The spiral approach to the Sun and the short final orbit Solar Probe 24 times the sun will come close instead of only twice, as it was planned in the original Solar Probe. However, due to the larger minimum distance from the Sun compared to the Solar Probe thermal radiation is only 1/16 of the value that would have been achieved with Solar Probe. This is sufficient for Solar Probe a plate-shaped sun shield with 2.7 m diameter and 17 cm thickness, the sun -facing side has to withstand approximately 1430 ° C. The probe body is constantly in the shadow of the sun shield. For the power supply has Solar Probe two different solar systems. The primary solar cells are on two, seated on opposite sides, two-part solar wings to be swung back when approaching the sun to keep its temperature below 180 ° C up to 75 °. When voltage drops below 0.25 AU distance from the Sun, they can, like at the start, to be completely retracted. Thereafter, the two secondary high-temperature solar panels, which protrude on opposite sides behind the sunscreen, the power supply. They are liquid cooled from the back and be fed during the approach to the sun. The scientific data are transmitted in the Ka-band with a parabolic antenna at the end of a retractable mast, which is folded back when it falls below 0.59 AE in the shadow of the sun shield. Thus, all measurement results of the near- solar flybys must be stored on board before the antenna can be extended again, to transfer them to the earth. Also enjoys Solar Probe nor X-band omnidirectional antennas to transmit telemetry and reception of control signals that remain constantly in the shadow of the sun shield. The take-off mass of Solar Probe will be 610 kg.
Design changes
In accordance with recent images and animations ( end of 2009 ) on the website of the JHU - APL, Solar Probe will now receive a hexagonal sun shield with rounded corners, which is wider at the two sides on which the solar panels are mounted as to the other. The solar paddles are only one part and the secondary solar arrays are gone. Your solar panels are now seemingly at the end of the back folding solar panels on a narrow angled surface that show after folding back the majority of the two solar panels in the shade of the sun shield to the sun.