The Parker Solar Probe is on its way

[lpetrich]

NASA launches Parker Solar Probe toward the sun - YouTube, NASA, ULA Launch Parker Solar Probe on Historic Journey to Touch Sun | NASA

It was launched by a Delta IV Heavy rocket on 3:31 AM EDT from Cape Canaveral, a day after the scrubbing of its previous launch attempt.

Heliophysics pioneer watches Liftoff of Parker Solar Probe | NASA -- Dr. Eugene Parker himself, after whom the spacecraft was named.

Parker Solar Probe describes the spacecraft in detail. It is to approach to a distance of 9 solar radii from the Sun's center or 0.04 AU, thus giving it a chance to sample the Sun's outer corona, where the corona fades off into the solar wind. This will be much closer than any previous spacecraft has gone. Helios A and Helios B both reached 0.3 AU, closer than planet Mercury, and the previous record for proximity to the Sun.

The PSP will have a carbon-composite sunshield that will get as hot as 2500 F / 1400 C at closest approach -- hot enough to glow. Its solar panels will folded inward, being shaded by the sunshield, at closest approach, and unfolded outward when farther away.

The PSP will do 24 orbits over its mission, and it will receive 7 gravity assists from Venus flybys. Its first flyby will be on October 2, and its first perihelion on November 5 at 36 solar radii or 0.17 AU. It will do a few orbits, then fly by Venus again, then repeat until it is in its final orbit. In that orbit, its perihelion will be as close as the PSP will get to the Sun, while its aphelion will be at Venus's orbit, about 0.72 AU away.

 

[lpetrich]

Planetary Society on Twitter: "We love this tribute to @NASASun's #ParkerSolarProbe by @timelapsejunkie… " -- nice video of the launch from a distance.

 

[Worldtraveller]

I think this will definitely be one of the more interesting scientific missions we've done recently.

 

[Loren Pechtel]

Of course it was a night launch. Otherwise it would be fried!

 

[lpetrich]

Parker Solar Probe Successfully Completes First Venus Flyby – Parker Solar Probe -- on October 3, the spacecraft traveled to 1500 mi / 2400 km of that planet. That is so the PSP can slow down so it can get closer to the Sun. It will be making six more Venus flybys before reaching its final orbit.

 

[Loren Pechtel]

Parker Solar Probe Successfully Completes First Venus Flyby – Parker Solar Probe -- on October 3, the spacecraft traveled to 1500 mi / 2400 km of that planet. That is so the PSP can slow down so it can get closer to the Sun. It will be making six more Venus flybys before reaching its final orbit.

It's still in flight? Wasn't this supposed to be a night trip to keep from melting?

 

[skepticalbip]

Parker Solar Probe Successfully Completes First Venus Flyby – Parker Solar Probe -- on October 3, the spacecraft traveled to 1500 mi / 2400 km of that planet. That is so the PSP can slow down so it can get closer to the Sun. It will be making six more Venus flybys before reaching its final orbit.

It's still in flight? Wasn't this supposed to be a night trip to keep from melting?

It seems that the trip to the sun would need to be during the day so the probe could see where it is going. But then certainly they would wait until night, when it is cooler, for landing.

 

[lpetrich]

I've found Parker Solar Probe at Johns Hopkins University. "The Mission" shows where the spacecraft is now, just inside Mercury's orbit.

On Sep 25, a little before its first Venus flyby, the spacecraft looked back: Parker Solar Probe:: Parker Solar Probe Looks Back at Home (also at Parker Solar Probe Looks Back at Home | NASA). The Earth looks like a bright star with a bump on one side -- the Moon.

 

[skepticalbip]

Hey, I can see my house..



A close-up of Earth from WISPR's Sept. 25, 2018, image shows what appears to be a bulge on our planet’s right side — this is the Moon.
Credit: NASA/Naval Research Laboratory/Parker Solar Probe

 

[bilby]

Hey, I can see my house..

View attachment 18453

A close-up of Earth from WISPR's Sept. 25, 2018, image shows what appears to be a bulge on our planet’s right side — this is the Moon.
Credit: NASA/Naval Research Laboratory/Parker Solar Probe

[YOUTUBE]https://www.youtube.com/watch?v=i7eqjiRRIqg[/YOUTUBE]

 

[lpetrich]

Parker Solar Probe Breaks Record, Becomes Closest Spacecraft to Sun | NASA

Parker Solar Probe now holds the record for closest approach to the Sun by a human-made object. The spacecraft passed the current record of 26.55 million miles from the Sun's surface on Oct. 29, 2018, at about 1:04 p.m. EDT, as calculated by the Parker Solar Probe team.

Me: that's 42.73 km or 0.2858 AU, closer than Mercury's perihelion distance of 0.3 AU.

Some asteroids approach closer than Mercury, though they spend most of their time farther out. Asteroids like Icarus (closest approach: 0.2 AU) and 2005 HC4 (closest approach: 0.071 AU).

The previous record for closest solar approach was set by the German-American Helios 2 spacecraft in April 1976. As the Parker Solar Probe mission progresses, the spacecraft will repeatedly break its own records, with a final close approach of 3.83 million miles from the Sun's surface expected in 2024.

Helios 2's record was 0.29 AU, and the PSP's closest approach is set to be 6.16 million km or 0.0412 AU

“It’s been just 78 days since Parker Solar Probe launched, and we’ve now come closer to our star than any other spacecraft in history,” said Project Manager Andy Driesman, from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “It’s a proud moment for the team, though we remain focused on our first solar encounter, which begins on Oct. 31.”

Parker Solar Probe is also expected to break the record for fastest spacecraft traveling relative to the Sun on Oct. 29 at about 10:54 p.m. EDT. The current record for heliocentric speed is 153,454 miles per hour, set by Helios 2 in April 1976.

That's 246,960 km/h or 68.6 km/s.

 

[lpetrich]

Parker Solar Probe:: All Systems Go As Parker Solar Probe Begins Second Sun Orbit It will make its closest approach to the Sun on April 4 and September 1 of this year, and it will fly by Venus again on December 26.

ESA Science & Technology: Solar Orbiter -- From Its mission summary,

Scheduled for launch in February 2020, the mission will provide close-up, high-latitude observations of the Sun. Solar Orbiter will have a highly elliptic orbit – between 1.2AU at aphelion and 0.28AU at perihelion. It will reach its operational orbit just under two years after launch by using gravity assist manoeuvres (GAMs) at Earth and Venus. Subsequent GAMs at Venus will increase its inclination to the solar equator over time, reaching up to 24° at the end of the nominal mission (approximately 7 years after launch) and up to 33° in the extended mission phase.

Not as close as the Parker Solar Probe will go, but it will be well away from the Sun's equator.

The Sun's equator is tilted about 6 degrees to the average orbit plane of the known planets. Here is a recent hypothesis for that oddity: Curious Tilt of the Sun Traced to Undiscovered Planet | Caltech [1607.03963] Solar Obliquity Induced by Planet Nine

 

[lpetrich]

•  Parker Solar Probe
• Parker Solar Probe | NASA
• Parker Solar Probe
• Parker Solar Probe:: Parker Solar Probe Touches the Sun for the First Time, Bringing New Discoveries
• Parker Solar Probe Completes a Record-Setting Swing by the Sun – Parker Solar Probe
• NASA Enters the Solar Atmosphere for the First Time | NASA

Touching the Sun?

From the "enters the solar atmosphere" article,

Unlike Earth, the Sun doesn’t have a solid surface. But it does have a superheated atmosphere, made of solar material bound to the Sun by gravity and magnetic forces. As rising heat and pressure push that material away from the Sun, it reaches a point where gravity and magnetic fields are too weak to contain it.

That point, known as the Alfvén critical surface, marks the end of the solar atmosphere and beginning of the solar wind. Solar material with the energy to make it across that boundary becomes the solar wind, which drags the magnetic field of the Sun with it as it races across the solar system, to Earth and beyond. Importantly, beyond the Alfvén critical surface, the solar wind moves so fast that waves within the wind cannot ever travel fast enough to make it back to the Sun – severing their connection.

It was previously estimated at 10 - 20 solar radii or 7 to 14 million kilometers (gigameters: Gm).

On April 28, 2021, during its eighth flyby of the Sun, Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii (around 8.1 million miles) above the solar surface that told scientists it had crossed the Alfvén critical surface for the first time and finally entered the solar atmosphere.

...
During the flyby, Parker Solar Probe passed into and out of the corona several times. This is proved what some had predicted – that the Alfvén critical surface isn’t shaped like a smooth ball. Rather, it has spikes and valleys that wrinkle the surface. Discovering where these protrusions line up with solar activity coming from the surface can help scientists learn how events on the Sun affect the atmosphere and solar wind.

There were two flybys since then. No word on them.

 

[lpetrich]

The mission:

• 2018 Aug 12: Launch -- distance 151.6 Gm / 1.013 AU / 217.9 Rsun, perihelion velocity --, orbit period 174 days
• 2018 Oct 3: Venus flyby #1
• 2018 Nov 6: Perihelion #1 -- dist 24.8 Gm / 0.166 AU / 35.6 Rsun, PH vel 95 km/s, per 150 d
• 2019 Apr 4: PH #2 -- Sep 1: PH #3
• 2019 Dec 26: VF #2
• 2020 Jan 29: PH #4 -- dist 19.4 Gm / 0.130 AU / 27.9 Rsun, PH vel 109 km/s, per 130 d
• 2020 Jun 7: PH #5
• 2020 Jul 11: VF #3
• 2020 Sep 27: PH #6 -- dist 14.2 Gm / 0.095 AU / 20.4 Rsun, PH vel 129 km/s, per 112.5 d
• 2021 Jan 17: PH #7
• 2021 Feb 20: VF #4
• 2021 Apr 29: PH #8 -- dist 11.1 Gm / 0.074 AU / 16.0 Rsun, PH vel 147 km/s, per 102 d
• 2021 Aug 9: PH #9
• 2021 Oct 16: VF #5
• 2021 Nov 21: PH #10 -- dist 9.2 Gm / 0.061 AU / 13.2 Rsun, PH vel 163 km/s, per 96 d
• 2022 Feb 25: PH #11 -- Jun 1: PH #12 -- Sep 6: PH #13 -- Dec 11: PH #14 -- 2023 Mar 17: PH #15 -- Jun 22: PH #16
• 2023 Aug 21: VF #6
• 2023 Sep 27: PH #17 -- dist 7.9 Gm / 0.053 AU / 11.4 Rsun, PH vel 176 km/s, per 92 d
• 2023 Dec 29: PH #18 -- 2024 Mar 30: PH #19 -- Jun 30: PH #20 -- Sep 30: PH #21
• 2024 Nov 6: VF #7 -- final Venus flyby
• 2024 Dec 24: PH #22 -- dist 6.9 Gm / 0.046 AU / 9.9 Rsun, PH vel 192 km/s, per 88 d -- final orbit
• 2025 Mar 22: PH #23 -- Jun 29: PH #24 -- Sep 15: PH #25 -- Dec 12: PH #26

Venus flybys #1, #2 are at the same place in the planet's orbit. Likewise for #3, #4, and for #5, #6

 

[lpetrich]

Parker Solar Probe Offers Stunning View of Venus | NASA

"During the mission’s third Venus gravity assist on July 11, 2020, the onboard Wide-field Imager for Parker Solar Probe, or WISPR, captured a striking image of the planet’s nightside from 7,693 miles away. (12,381 km, about 2 Venus or Earth radii)

WISPR is designed to take images of the solar corona and inner heliosphere in visible light, as well as images of the solar wind and its structures as they approach and fly by the spacecraft. At Venus, the camera detected a bright rim around the edge of the planet that may be nightglow — light emitted by oxygen atoms high in the atmosphere that recombine into molecules in the nightside. The prominent dark feature in the center of the image is Aphrodite Terra, the largest highland region on the Venusian surface. The feature appears dark because of its lower temperature, about 85 degrees Fahrenheit (30 degrees Celsius) cooler than its surroundings.

That aspect of the image took the team by surprise, said Angelos Vourlidas, the WISPR project scientist from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, who coordinated a WISPR imaging campaign with Japan’s Venus-orbiting Akatsuki mission. “WISPR is tailored and tested for visible light observations. We expected to see clouds, but the camera peered right through to the surface.”

“WISPR effectively captured the thermal emission of the Venusian surface,” said Brian Wood, an astrophysicist and WISPR team member from the U.S. Naval Research Laboratory in Washington, D.C. “It’s very similar to images acquired by the Akatsuki spacecraft at near-infrared wavelengths.

WISPR was designed for visible light, but it is also sensitive to near-infrared?

 

[Shadowy Man]

Parker Solar Probe Offers Stunning View of Venus | NASA

"During the mission’s third Venus gravity assist on July 11, 2020, the onboard Wide-field Imager for Parker Solar Probe, or WISPR, captured a striking image of the planet’s nightside from 7,693 miles away. (12,381 km, about 2 Venus or Earth radii)

WISPR is designed to take images of the solar corona and inner heliosphere in visible light, as well as images of the solar wind and its structures as they approach and fly by the spacecraft. At Venus, the camera detected a bright rim around the edge of the planet that may be nightglow — light emitted by oxygen atoms high in the atmosphere that recombine into molecules in the nightside. The prominent dark feature in the center of the image is Aphrodite Terra, the largest highland region on the Venusian surface. The feature appears dark because of its lower temperature, about 85 degrees Fahrenheit (30 degrees Celsius) cooler than its surroundings.

That aspect of the image took the team by surprise, said Angelos Vourlidas, the WISPR project scientist from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, who coordinated a WISPR imaging campaign with Japan’s Venus-orbiting Akatsuki mission. “WISPR is tailored and tested for visible light observations. We expected to see clouds, but the camera peered right through to the surface.”

“WISPR effectively captured the thermal emission of the Venusian surface,” said Brian Wood, an astrophysicist and WISPR team member from the U.S. Naval Research Laboratory in Washington, D.C. “It’s very similar to images acquired by the Akatsuki spacecraft at near-infrared wavelengths.

WISPR was designed for visible light, but it is also sensitive to near-infrared?

That appears to be what they are claiming. I took a look at their optical design website and there isn’t quite enough information for me to be absolutely sure why. THey are using cmos detectors, which could have some sensitivity out into the 2 micron range and it’s not clear if they are using any band pass filters or what the transmissions of the lens materials are. Perhaps they just figured that the visible light would dominate over any potential “red leaks” so they didn’t concern themselves about it. But then looking at the night side of Venus what sensitivity they may have in the infrared allowed them to pick up the emission.

 

[lpetrich]

Seems like it. They are now researching the infrared sensitivity of WISPR. Since they know how they built it, they can build duplicates of it, if they had not already done so for other tests.