Screenshot from NASA Webcast of the launch of Solar Orbiter. NASA had a clock on screen then
Mission Rundown: ULA - Atlas V 411 - Solar Orbiter
Written: September 10, 2021 - Edit: November 28, 2022
Let’s go catch some rays
ESA's Solar Orbiter spacecraft was launched on 10 February 2020 (04:03 GMT) by a NASA-provided Atlas-V 411 vehicle of ULA, designated AV-87, from KSC (Kennedy Space Center) SLC-41 (Space Launch Complex), Cape Canaveral, FL, USA.
During the two-hour launch window, there were 25 instantaneous opportunities — a single second launch every 5 minutes — in which Atlas V could launch with a new azimuth owing to the ever-changing trajectories needed to insert Solar Orbiter into an interplanetary transfer heliocentric orbit to Venus.
We are going back to our star!! Solar Orbiter is a spacecraft built by the European Space Agency, ESA to study the inner heliosphere and its overall effects on solar radiation. Solar Orbiter is on a 3.5 year journey to the Sun.
Atlas V 411’s first number/letter shows the fairing diameter size in meters. The number 4 obviously means a 4,2 meter fairing. The second number determines the number of strap on solid rocket boosters (SRBs). It can range from 0 to 5, and in this case, there is only one on the side of the center core. The third and final number refers to the number of engines on the Centaur Upper Stage, which can be either one or two.
What goes up must come down. In about 4 minutes the Atlas V delivers a mighty kick to the main Centaur second stage, and after stage separation it will coast 2100 km further downrange. link
In this case there will be one engine ‘Bell or Nozzle’. The only time that there have been two engines on an Atlas V was on Starliner’s OFT-1. Technically it was on the Centaur.
The diagram above shows a detailed simulation of just how far this booster ‘ 1st stage’ will travel before crashing down into the Atlantic Ocean after Main Engine Cut-Off (MECO) and the Centaur upper stage ignites on its way to orbit. Thanks to Declan from FlightClub for doing this specially for this article!
Here it’s evident that Atlas V kicks the full weight of Centaur upper stage, the fairings and the payload about 120 km skyward and 300 km downrange before accepting its faith as a suborbital rocket under command of gravity. Maybe ULA should sell seats on the Atlas V interstage. That's one hell of a ride. Extra SRB’s and spacesuits should do it.
Initial parking orbit for this mission is 203 x 236 km. This is the orbit Centaur will initially inject into for its ~30 minute coast until Centaur re-ignition for the injection to heliocentric orbit bound for Venus.
The Solar Orbiter
Photo of Solar Orbiter on its service mount. Note the angle and rotation. By Jacques Van Oene
The Solar Orbiter will use Venus gravity assists to obtain the high inclinations reaching 35º with respect to the sun's equator (inclined elliptical orbit) at the end of the cruise phase mission (the cruise phase will last about 3.4 years).
Using SEPM (Solar Electric Propulsion Module) in conjunction with multiple planetary swing-by maneuvers, it will take the Solar Orbiter only two years to reach a perihelion of 45 solar radii with an orbital period of 149 days.
Within the nominal 5 year mission phase, the Solar Orbiter will perform several swing-by maneuvers at Venus, in order to increase the inclination of the orbital plane to 30º with respect to the solar equator. During an extended mission phase of about two years, the inclination will be further increased to 38º.
During the initial cruise phase, which lasts until November 2021, Solar Orbiter will perform two gravity-assist maneuvers around Venus and one around Earth to alter the spacecraft's trajectory, guiding it towards the innermost regions of the Solar System. At the same time, Solar Orbiter will acquire in situ data and characterize and calibrate its remote-sensing instruments. The first close solar pass will take place in 2022 at around a third of Earth's distance from the Sun.
Solar Orbiter carries ten science instruments
– nine are led by ESA Member States and one by NASA – all working together in close collaboration to provide unprecedented insight into how our local star ‘works'. Some are remote-sensing instruments that look at the Sun, while others are in-situ instruments that monitor the conditions around the spacecraft, enabling scientists to ‘join the dots' from what they see happening at the Sun, to what Solar Orbiter ‘feels' at its location in the solar wind millions of kilometers away.
During some sections of its orbit, it will be able to work in cooperation with NASA’s Parker Solar Probe currently in orbit around our sun. There are four main questions that Solar Orbiter is trying to answer:
What drives the solar wind and where does the coronal magnetic field originate from?
How do solar transients drive heliospheric variability?
How do solar eruptions produce energetic particle radiation that fills the heliosphere?
How does the solar dynamo work and drive connections between the Sun and the heliosphere?
It will be able to do this with a multitude of onboard instruments. Some of the in-situ instruments include a Magnetometer (MAG), a Radio and Plasma Waves detector (RPW), a Solar Wind plasma Analyser SWA, and an Energetic Particle Detector (EPD).
Another set of instruments in the group are remote sensing. These include:
STIX: X-ray Spectrometer/Telescope
SPICE: Spectral Imaging of the Coronal Environment
SoloHI: Heliospheric Imager, PHI: Polarimetric and Helioseismic Imager
METIS: Coronagraph
EUI: Extreme Ultraviolet Imager
ESA Solar Orbiter link to instruments. Solar Orbiter's instruments can talk to each other. If one sees something interesting, it can flag the other instruments to go look at the same thing in real time.
Like Parker Solar Probe, Solar Orbiter's instruments 'hide' behind the heat shield to protect them. But there are doors on the heat shield that will open during perihelion passes to allowed direct photos and readings.
This Atlas V 411 configuration vehicle includes a 4,2 meter large payload fairing (PLF) and stands 189 feet - 57,6 meter tall. The Atlas booster for this mission is powered by the RD AMROSS RD-180 engine. Aerojet Rocketdyne provided the one AJ-60A SRB and RL10A-4-2 engine for the Centaur upper stage.
With only one SRB and the low payload weight, Atlas V 411 is powerful enough to loft this mission. Solar Orbiter requires a precise orbital injection, including a very specific C3 of 31.05 km^2/s^2. So the Atlas 411 is the perfect size.
C3 is the Characteristic energy. It tells you if a space vehicle has enough energy to escape the gravitational influence of a body and what shape, parabolic or hyperbolic, the escape trajectory will be. This is a standard orbital parameter for interplanetary missions.
Solar Orbiter trajectory from Earth launch to orbit the Sun assisted by Venus (image credit: ESA)
The spacecraft's orbit has been chosen to be ‘in resonance' with Venus, which means that it will return to the planet's vicinity every few orbits and can again use the planet's gravity to alter or tilt its orbit. Initially Solar Orbiter will be confined to the same plane as the planets, but each encounter of Venus will increase its orbital inclination.
For example, after the 2025 Venus encounter it will make its first solar pass at 17º inclination, increasing to 33º during a proposed mission extension phase, bringing even more of the polar regions into direct view.
From its launch early in 2017, the Solar Orbiter will reach the nominal orbit around the Sun in 2020, operating in its near-Sun environment for at least 6 years, including the extended mission phase. During this period, the spacecraft will carry the science payload through 14 perihelion passages. At the same time, the heliocentric latitude will be gradually increased through repeated Venus gravity assist maneuvers, providing information about the behavior of the Sun at high latitudes.
Daddy. What’s on top of the Sun?
The Atlas V 411 rocket
The 189 feet tall launch vehicle tasked with sending the Solar Orbiter on its way to Venus was the United Launch Alliance Atlas V rocket flying and its 411 configuration.
This mission was the 82nd flight of the Atlas V and the sixth of its 411 configuration.
The Atlas V 411 rocket configuration is flying with a 4-meter payload fairing, a single solid rocket booster AJ-60A, and a single RL-10A-4-2 engine on Centaur upper stage.
Atlas V went through a test called a Wet Dress Rehearsal for a reason. Fueling has begun at Space Launch Complex-41 to load the rocket with 66,000 gallons of cryogenic liquid oxygen and liquid hydrogen as ULA tests the ‘day-of-launch’ operations.
The single side-mounted solid rocket booster creates a ‘slide’ with a tremendous amount of asymmetrical thrust that must be compensated for by the Thrust Vector Control - TVC systems on the Atlas V booster itself.
The RD AMROSS RD-180 on the Atlas V 411 is progressively gimballed to counteract the asymmetrical thrust of the single solid rocket, allowing Atlas V to fly a straight trajectory. This however wastes some of the thrust going straight down.
For launch, the RD-180 engine was commanded to ignite at T-2.7 seconds.
At T0, the single solid rocket was lit and Atlas V lifted off.
After power-sliding off the pad and ascending close through SLC-41’s lightning protection system towers and wires, the Atlas V performed a pitch and roll maneuver to align itself onto its azimuth – trajectory – for a flight to the east-southeast of Cape Canaveral.
The azimuth, in this case, will not be due east based on the position Centaur needs to obtain in Earth parking orbit before reigniting its engine to inject Solar Orbiter into a Venus-transfer heliocentric (Sun) orbit. Solar Orbiter won’t care about from where on Earth’s surface it aims for the Venus predicted position in its orbit.
No pre-planned launch schedule was found.
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