As this article is being published, the Parker Solar Probe just flight over Venus and is always heading to its target, the Sun. Of course, the probe left the Earth two months ago, but we will use this event to review its mission.
Introduction: The Living With a Star program
Few years ago, NASA begun the Living With a Star program, which the Parker Solar Probe is a part of.
This program aims to study our star, the Sun.
Because yes, even if it is the nearest star, we don’t know very much things about it, its activity and its storms! To complete successfully its studies, NASA had already built two scientific satellites that are only orbiting Earth.For example, they study the solar winds in the radiation belt that surround usor they watch directly the Sun in various light spectrums.
But, if you want to understand a star,you don’t only need to watch it from far away, you have to come as close as possible.And this is wherethe Parker Solar Probe is needed.
Let’s go back to the Parker Solar Probe.
In order to study the Sun (and most particularly its corona) from very close, it will be positioned to a high elliptic orbit around the Sun, with a distance at the perihelion (closest point from the Sun of the orbit) of 24 million kilometres at the beginning of the mission, then less than 6.5 million kilometres at the end of it.
That could seem pretty farbut the temperature already reaches hundreds of degrees.That way, the probe needs a really good solar protection.Its mission will be to study the solar corona by flying as close as possible from the Sun with various scientific equipment. We will take a closer look later.
Communications, cooling and motion control
The Parker Solar Probe is not very big,its body is only 1 by 2 metres. However, in order for it to resist to the very high solar heat, it has been equipped with a massive thermal shield. So, it had its sized multiplied by two. This shield is 2.3 metres wide and only 12 centimetres thick.
It was built with carbon composite and cover with aluminium oxide, more often called alumina. Add to that4 radiators, used to dissipate the heat, and so, to avoid the overheating of the electrical parts, via a liquid cooling system.These 12 little centimetres of thermal protection, paired with the radiators,are really efficient to keep the probe to -250°C while the shield is over 1150°C, a difference of more than 1400°C!
In order to control its orientation (it needs to always keep its shield facing the Sun), and also its altitude the probe has 12 small engines propelled by hydrazineand 4 reaction wheels. It locates itself with star’s coordinates and also two gyroscopes. The probe, with 55 kilogrammes of fuel, can increase its speed of 170 metres per second during its whole mission.
To communicate with the Earth, even far away, the Parker Solar Probe has a high gain parabolic antenna (high amplification of the signal), and many small low gain antenna (low amplification). The contact and the data transmission will only be done further than 0.25 astronomic units from the Sun, to avoid the electromagnetics disturbances from the solar activity.
Don’t forget that this probe has a very important mission, unlock the secrets of the Sun. So, to study it, the probe gets on board a multitude of sensorsand other scientific instruments.
Firstly, there is FIELDS. FIELDS is a device that measure the electro-magnetic field, the plasma wave and the radio wave from the Sun. It has various antennas, including 5 that measure the electrical voltage and 3 for the electro-magnetic field. For of them are attached to the side of the thermal shield, and so,they need to be very resistant to the solar heat.
Then, there is SWEAP that means Solar Wind Electrons Alphas and Protons. Its sensors were all conceived and built by the university of Michigan and the astrophysical centre of Harvard. This tool has three sensors SPAN-A, SPAN-A+ and SPAN-B, that measure the electrons and the ions that are in the solar winds, but also a fourth one that is called SPC, a Faraday cup that measure the entrance speed of the solar wind particles in the probe.
The third instrument, WISPR, is the only imaging device on the probe. It has the size of a shoebox and it will have the big task to observe the solar corona and the intern heliosphere. It has two telescopes, in order to have a wide field of view and, at the same time, images with a good definition. The shield will have an important part in the working of WISPR :indeed, it will have to hide the Sun when the images will be captured.
Finally, let’s talk about ISIS. Its task will be to observe some particles like protons, neutrons or ionized atoms on a very wide energetic range that are mysteriously speed up in outer space, and try to understand it.It has two small particle sensors to do its measures, EPI-Lo and EPI-Hi (EPI means Energetic Particle Instrument).
We have finished to study the anatomy of this so much important orbiter.Now, let’s focus on the steps of its mission.
Currently, the Parker Solar Probe is in the interplanetary space, not far from Venus. But, let’s start chronologically, simple question of logic!
At the beginning: the launch. Originally, it should have happened in August, the 11th, with a Delta IV Heavy rocket. However, only a moment before the launch, countdown was frozen because of a pressure issue of gaseous helium. Unfortunately, when the problem was solved, it was already too late, the launch window had been closed. So, the NASA, and ULA (the company that uses the rocket) delayed the launch for the day after.
So, August, the 12th, 9:36 am (UTC), in the Floridian night, we finally had the opportunity to see the rocket take offwithout any trouble! By the way, Eugene Parker, the astrophysicistthat gave its name to the probe because of its many works on the Sun, assisted to the take off. And we heard that he loved the show!
Today (October 3rd), after 2 months of travel, the probe arrived finally above Venus. It will use its gravitational attraction to reduce the altitudeof its orbit, to come as close as possible to the Sun, firstly to 24.8 million kilometres. During its mission, it will use this method 7 times, in order to always come closer to the Sun.
Then, November, the 5th, the probe will be for the first time at the perihelion;in other words, the lower point of its orbit, at approximately 35 solar radiuses to its target. It will be the first time that it will be able to carry out some measures close to the Sun.
During its mission, that will end in 2025, the probe will fly over Venus 6 more times, orbit 24 times the Sun, fly less than 7 million kilometres from the Sun, will face very high temperature et and will become the fastest human object, with a top speed of 197 km/s. What a program for a such little probe with a huge scientific potential!
Thank you for reading this article,
Arnaud (fr), Nodyrus (translation)