I2S - Lecture 1-3 Flashcards
Which spacecraft crossed the boundaries of the heliosphere in interstellar space?
Voyager, (approx. 23.5 billion km)
What do satellites do?
- GNSS (navigation)
- Meteorology
- Earth observation
- Telecommunications
- Interplanetary Explorations
What are aspects of the in-space economy?
Maintenance, Life Extension, Refuelling, Upgrade, Fuel Depots, Closed-Loop Life Support, Proximity Operations, Manufacturing, Assembling, Debris Removal, Recycling, In-Situ resource utilization
What are the heights of typical orbits?
LEO - 200 to 2000km
MEO - 2000 to <36000km
GEO - 35786km
SSO - 600 to 800km
GTO - 200 to 800 (P) - 36000km (A)
State Kepler‘s laws and explain them shortly.
- Law: Each planet‘s orbit about the sun is an ellipse, sun center is always located at a focus
- Law: the imaginary line joining a planet and the Sun sweeps equal areas of space during equal time intervals
3.Law: squares of orbital periods of the planets are directly proportional to the cubes of the semi-major axis of their orbits
What mean temperature do the planets of the solar system have?
- Venus: 737K
- Mercury: 440K
- Earth: 288K
- Mars: 208K
- Jupiter: 163K
- Saturn: 133K
- Uranus: 78K
- Neptune: 72K
- (Pluto: 47K)
State Newton‘s Law of Universal Gravitation, and what it describes.
The gravitational force between two masses having a distance r between their centers.
F_g = G * ( (m1*m2) / r^2
[ for an object on the surface of the Earth: g_0 = G*(m_Earth / r_Earth^2 ) ]
What are Exoplanets?
An exoplanet is any planet beyond our solar system. Most of them orbit other stars, but some free-floating exoplanets, called rogue planets, are untethered to any star.
How many exoplanets are confirmed, and what classes are there?
We have confirmed more than 5600 exoplanets (NASA).
Gas Giant (30%)
Super-Earth (31% - size range between Earth and Neptune)
Terrestrial (4% - small rocky planets)
Neptune-like (35% - ice giants or warmer)
State some „exoplanet-sensitive“ missions
Ariel (ESA), Plato(ESA), Webb (NASA/ESA), Cheops (ESA), Tess (NASA), Gaia (ESA), Kepler/K2 (NASA), Corot (ESA), Spitzer (NASA), Hubble (NASA/ESA)
How do we detect exoplanets? (Short)
- Transit photometry (variation of brightness of stars)
- Transit-timing variation (measuring of orbital periods)
- Radial velocity (shift of wavelength)
- Microlensing (anomalies in brightness)
- Astrometry (Position in the sky over time)
- Direct imaging
*What is space weather?
- Solar weather, is the dynamical transfer of energy from the Sun to the Earth in the form of solar photons, charged particles, and fields that vary on multiple time and spatial scales
- Cosmic weather, ….
Does the solar weather varies over time?
Yes, solar activity varies constantly. Furthermore solar activity increases significantly in a 11-year solar cycle.
Does the surface of the sun have a constant rotation speed?
No, it exhibits differential rotation, this means that different parts of the Sun rotate at different rates.
The rotation speed varies gradually between the equator (25 days/rotation) and the poles (35 days).
What happen to the incoming solar wind? (-> earth)
When the solar wind encounters Earth, it is deflected by our planet’s magnetic shield, causing most of the solar wind’s energetic particles to flow around and beyond us. This region that meets and blocks the solar wind is called the magnetosphere.
What is a CME?
Coronal Mass Ejection
They are large expulsions of plasma and magnetic field from the Sun’s corona. They can eject billions of tons of coronal material, at speeds up to 3000 km/s
What is the corona?
The Sun’s corona is the outermost part of the Sun’s atmosphere. The corona is usually hidden by the bright light of the Sun’s surface.
What effect have solar wind on technology?
It can disrupt satellites power grid, and communications on earth.
(Also induces drag on satellites)
How are solar flares created?
4 Steps
- Sun’s magnetic field lines run from sout to north between the poles
- Rotation causes field lines to stretch, more so at the equator which rotates faster than the poles
- Field lines become twisted and some eventually burst trough the surface to form loops
- When the loop grows past a critical point, it blasts away from the sun forming a solar storm
What are the Van Allen belts?
The Earth’s magnetosphere traps the high energy radiation particles and shields the Earth from the solar storms.
These trapped particles form two belts of radiation, known as the Van Allen Belts, that surround the Earth like enormous donuts
https://science.nasa.gov/biological-physical/stories/van-allen-belts/
What are the units of radiation?
- Gray (Gy): SI unit: amount of radiation that deposits 1 J/kg in a material
- Rad: 100 Rads = 1 Gy
- Dose: amount of radiation energy deposited in a material as a function of time
What are common energy levels of radiation?
Human-made, Solar, Radiation belts, Galactic
- Human-produced: up to 108eV
- Solar energetic photons: from solar events 108eV
- Radiation belts: up to 109eV
- Solar energetic particles (SEP): during CME, 1011eV
- Galactic cosmic rays: 1021eV
Which impacts on operations can space weather have?
- Earth-orbiting (EO) = location knowledge, pointing precision and gas supply
- Deep Space (DS) = pointing precision and gas supply
- End-of-life (EL) = end of life timing and location
What effect has radiation on solar arrays?
Radiation decreases both current and voltage, leading to lower performance as initial
