Friday 1st October 2021, The BepiColombo Spacecraft passed Mercury at a distance of 199 KM / 123 miles

Mercury.

Friday 1st October 2021, the BepiColombo spacecraft passed Mercury at a distance of 199 KM / 123 miles, the engineering cameras and many of the scientific instruments were used to gather new images and data on The First Rock from the Sun. Fantastic images, very high quality. 

The first Hermean science has been released from this encounter from the science instruments used on board the BepiColombo spacecraft.  

The PHEBUS / Probing of Hermean Exosphere By Ultraviolet Spectroscopy, Ultraviolet Spectrometer sampled the extremely tenuous 'atmosphere' or Exosphere of Mercury. Detection of Hydrogen & Calcium were made as the BepiColombo spacecraft exited the deep shadow of Mercury. Whilst both had been observed before by the NASA / JHU / APL MESSENGER / MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft  during the hugely successful orbital mission, the PHEBUS on BepiColombo was able to determine that the exosphere was virtually non existent over the cryonically cold Hermean nightside. The suggests that it may well be produced by sunlight acting on the surface chemistry, releasing Hydrogen and Calcium atoms. 

The MGNS / Mercury Gamma-ray and Neutron Spectrometer detected peaks as the Gamma Rays from deep space dislodge neutrons and give of Gamma Rays from surface elements within Mercury's regolith and rocky material. This will reveal surface and near subsurface composition. This is being analyzed along with similar data from the Venus encounter back in August. 

The Magnetometer also returned useful scientific data. Whilst Mercury's magnetosphere had been well mapped particularly over the northern hemisphere by the NASA / JHU / APL MESSENGER / MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, during the orbital mission, BepiColombo got to sample it over Mercury's southern hemisphere closely. MESSENGER never closely approached Mercury's southern hemisphere as the spacecraft's Hermcentric (Mercury Centred) orbit was very eccentric (for thermal reasons as Mercury;s surface re-radiates a lot of the Sun's energy in infrared and this would over prolonged periods cause MESSENGER to malfunction), with the low Periherm (closest point to Mercury in a Mercury Centred orbit) was over the far northern hemisphere as it was known that Mercury's northern hemisphere had the most interesting geological features, such as the Caloris Basin, etc. MESSENGER was always too far from Mercury when over the southern hemisphere to properly map the magnetosphere. 

When BepiColombo eventually achieves Hermcentric orbit, BapiColombo Mercury Planetary Orbiter will stay in a 400 KM / 248 mile high orbit over the whole planet as the spacecraft has a different thermal protection system to that MESSENGER had. 

The Magnetometer detected Mercury's magnetosheath, the point immediately behind the Bow Shock were the solar wind crashes into Mercury's magnetosphere and the particles of the solar wind slow down and tumble before being deflected past Mercury. 

The ISA / Italian Spring Accelerometer, measures change of speed, and direction of the spacecraft. During this encounter, the ISA detected how the centre of gravity within BepiColombo changed very slightly as the solar arrays very slightly warped as the spacecraft entered and exited the deep. cryonically cold shadow of Mercury. Also the ISA detected the PHEBUS ultraviolet spectrometer, ping back into it's bracket after use.

The video below, also contains the solar wind and engineering data, being converted into sound (there is no sound in space, but fields and particle data as well as vibrations within the spacecraft can be converted to sound). The load 'clump' is the PHEBUS instrument clicking back into it's bracket after use.

https://dlmultimedia.esa.int/download/public/videos/2021/10/015/orig-2110_015_AR_EN.mp4

Sound of Mercury's magnetic field. The background tone measures the strength of the magnetosphere, deeper tone, stronger field. The  strength of the solar wind is measured by the variable higher pitched tone following the line. The dashed line represents Closest Approach, only 199 KM / 123 miles above the surface of the First Rock from the Sun. 

"https://www.youtube.com/embed/ZQAVXrlK0bs?rel=0" 

The encounter used the gravity of Mercury to slowly alter the trajectory and reduce the Heliocentric / Sun centred orbital speed towards Mercury, eventually with Hermcentric / Mercury centred orbital insertion on: Friday 5th December 2025.

This was the first of five Mercury encounters on: Saturday 2nd October 2021, BepiColombo passed @ a distance of only 199 KM / 123 miles..

Here various features are seen such as the Astrolabe Rupes under the rising Sun, craters Raphael, Flaubert, Haydn, Bramante and Smetana.

I love these images, give a real sense of being on a spacecraft. The high resolution science cameras were not available right now because they are mounted of the side that is stacked against the MTM (Mercury Transfer Module) but they will be available after the MTM and the MPO (Mercury Planetary Orbiter) separate during final approach in late 2025.

These engineering cameras are that, engineering monitoring, but they take fantastic images of parts of the spacecraft moving in front of the planets Mercury, Venus and Earth during encounters, looking like a space station or crewed craft passing by. Of course the science cameras do not give such a sense as they are obviously unobstructed in their field of views. 

Even if the science cameras were available, I would still use the engineering cameras too as they provide a very interesting, almost human viewpoint in addition to the science imagery.  

Mercury orbits the Sun once every 87 days, 23 hours and 18 minutes. The orbit around the Sun is quite elliptical and distance from the Sun varies from Perihelion, closest to the Sun @ 46,001,200 KM, mean distance of 57,909,050 KM and Aphelion, furthest from the Sun @ 69,816,900 KM.

Mercury rotates on its axis once every 58 days, 15 hours and 30 minutes. In relation to the Sun though takes 175 days, 22 hours and 36 minutes. Mercury rotates three times for every two orbits around the Sun.

Mercury has a diameter of 4,880 KM / 3,032 miles & a mass of 328.5 billion trillion tons (328.5 followed by twenty zeros).

The surface temperature at the equator varies from minus 186 Celsius at sunrise to 427 Celsius just after hermian noon. 

Our own Earth with a diameter of 12,742 KM / 7,917 miles, with a mass of 5,972.2 billion trillion tons (5,972.2 followed by twenty zeros) and a mean density of 5.517 G/CM3.

The following Mercury braking enounters will occur on: 

Thursday 23rd June 2022.

Tuesday 20th June 2023.

Thursday 5th September 2024.

Monday 2nd December 2024.

Thursday 9th January 2025.

Hermcentric orbital insertion:  Friday 5th December 2025.

End of Primary Mission: Saturday 1st May 2027.

End of possible extended mission: Monday 1st May 2028.

BepiColombo Launched successfully from Kourou, French Guiana: Saturday 20th October 2018 @ 01:45 GMT or Friday 19th October 2018 @ 22:45 GFT local time in French Guiana. Ariane 5. 

Flight: VA 245.

Text: Andrew R Brown.

ESA / JAXA Bepi-Colombo spacecraft.