Exam Prep Flashcards
(168 cards)
1
Q
What happens to acceleration during the launch of a satellite?
A
Acceleration increases toward the end of each stage’s operation.
2
Q
What type of environment is generated by rocket propulsion during a satellite launch?
A
A severe acoustic/vibration environment.
3
Q
What causes mechanical shocks during a satellite launch?
A
Events like explosive bolts, stage ignition, and docking.
4
Q
What thermal effect occurs during a satellite launch?
A
Heating due to aerodynamic friction.
5
Q
How does ambient atmospheric pressure change during a satellite launch?
A
It drops significantly (~4-5 kPa/s).
6
Q
What is electromagnetic interference (EMI) and how does it affect satellites during launch?
A
EMI can disrupt payload operations or ignite onboard propulsion systems.
7
Q
Which environmental factors are the most severe for the satellite?
A
Acoustic vibrations, mechanical shocks, and EMI are typically the most damaging, potentially causing structural or electronic failure
8
Q
What are the mechanical effects of the space environment?
A
Forces and torques from drag, gravity, solar wind, and magnetic fields; impacts from meteoroids and debris.
9
Q
What are the thermal effects of the space environment?
A
Heat exchange only occurs through EM radiation (absorption and emission); uneven heating can cause thermal stresses.
10
Q
What causes material degradation in space?
A
Radiation and vacuum cause fatigue and outgassing; atomic oxygen erosion in LEO damages surfaces.
11
Q
What are the effects of high-energy particles on electronics in space?
A
They can lead to single-event upsets, degradation, or failure.
12
Q
principal effects of the space environment on satellites
A
mechanical, thermal, material degredation and electronics
13
Q
environment factors acting on a satellite at LEO
A
Atmosphere drag, Atomic oxygen, Radiation and magnetic fields, Meteoroids and debris
14
Q
environment factors not essential at GEO
A
Atmosphere drag and atomic oxygen are negligible due to the vacuum at higher altitudes
15
Q
What is outgassing in the context of satellites?
A
Loss of volatile compounds from materials, leading to contamination.
16
Q
What is cold welding?
A
Metal surfaces in contact may bond.
17
Q
How does a vacuum affect material degradation in satellites?
A
Radiation and vacuum lead to brittleness and cracking.
18
Q
What is a positive effect of a vacuum on satellite materials?
A
Lack of moisture and oxygen prevents rusting.
19
Q
How can certain metals benefit from a vacuum in terms of crack closure?
A
Crack closure through cold welding improves fatigue life and material strength.
20
Q
negative effect of a vacuum on satellite materials and systems
A
Outgassing, Cold welding, Material degradation
21
Q
positive effect of a vacuum on satellite materials and systems
A
Corrosion resistance, Self-healing
22
Q
the effect of “self-healing” of some metals in a vacuum
A
metals like nickel can undergo cold welding, where cracks are “healed” by atomic bonding at the crack interface
23
Q
sources of high-energy particles
A
Solar flares, Van Allen belts, Cosmic rays
24
Q
effects of high-energy particles on Satellites
A
Electronic degradation, Material damage, Human risk
25
solar radiation mentioning all components of this radiation
Electromagnetic radiation: Visible light, UV, IR, X-rays, and gamma rays; Solar wind: Charged particles (protons and electrons) at high velocity; Solar flares: Intense bursts of radiation across the spectrum
26
structure of the terrestrial magnetic field
Resembles a dipole near the surface but distorted by solar wind further out. The Van Allen belts trap high-energy particles. The field has radial and tangential components depending on latitude and altitude
27
Effect of solar wind on the Earth's magnetic field
Compresses the field on the sun-facing side and elongates it on the opposite side, forming the magnetosphere. Variations in solar activity can disturb the magnetic field, causing geomagnetic storms.
28
Describe the problem with lubrication in space.
Lubrication can evaporate in space (outgassing) and is also affected negatively by the cold welding process.
29
Describe the sources of high energy particles and describe the effect of ionizing radiation on satellite systems.
Solar flares, van Allen radiation belts and cosmic rays are all sources of high energy particles. Rays can flip bits in electronic systems or cause biochemical damage.
30
Mention all components of solar radiation.
Solar radiation consists of 1.) EM Radiation and 2.) Plasma flux (solar wind + solar flares)
31
Describe the structure of the terrestrial magnetic field. How does the solar wind affect its structure?
The terrestrial magnetic fields consists of 1.) current in the earths core and 2.) currents caused by motions of ions and electrons in the magnetosphere. Solar wind plasma carries its own magnetic field, distorting the earths simple dipole field into shape
32
What hazard do meteoroids and material particles present to a satellite in orbit? What design is used to decrease the effect of meteoroid impact?
Material particles at high speed can cause physical damage to the satellite, compromising onboard systems, Impact shields such as Whipple shields can break apart meteoroids so they impact over a larger surface area.
33
Which environmental factor is most dangerous for a crew travelling to Mars?
X-ray radiation
34
Describe the Van Allen Belts
Layers of trapped charged particles within Earth's magnetic field. Inner belt: Protons (1,000-6,000 km).
Outer belt: Electrons (13,000-60,000 km).
These belts protect Earth but pose a radiation hazard to satellites and spacecraft
35
Describe the physical phenomenon lying in base of van Allen belt formation.
Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays.
36
Explain the South-Atlantic Anomaly, and it's effect on satellites.
A region where the inner Van Allen belt dips closest to Earth. Caused by the offset and non-uniformity of Earth's magnetic field.
Satellites experience higher radiation levels, leading to electronics degradation and increased single-event upsets
37
effects of south atlantic anomaly?
Satellites experience higher radiation levels, leading to electronics degradation and increased single-event upsets
38
Describe the origin of atomic oxygen and its effects on satellites.
Atomic oxygen forms in LEO due to the dissociation of molecular oxygen by UV radiation. These particles erode & corrode satellite materials.
39
Describe the evolution of an elliptic orbit effected by atmospheric drag at its perigee.
Drag slows the satellite, causing its perigee to lower further. The orbit becomes more circular over time.
Eventually spirals into denser atmosphere and burns up
40
What's the equation to calculate the time it takes for 1 particle to hit a satellite surface area, when given area A and flux ΔN?
t = 1/ (ΔN × A)
41
Describe the problem of near-zero gravity in a spacecraft and methods of its solution
Because of zero gravity, very small effects can lead to disturbance torques which create undesired satellite attitude changes:
* gravitation field slightly non- uniformity
* terrestrial magnetic field
* outgas (after the launch)
* solar radiation pressure
* antenna radiation pressure
42
What are the best orbit types for communications missions?
GEO for low latitudes, Molniya-Tundra orbits for high latitudes, Constellations of Polar LEO satellites for global coverage
43
What is the best orbit type for navigation missions?
Inclined MEO for global coverage
44
What is the best orbit type for earth observation missions?
Polar LEO for global coverage
45
What are the best orbit types for weather observation missions?
Polar LEO or GEO
46
What are the best orbit types for space observation/ astronomy missions?
LEO, HEO, GEO & L-points
47
What are the best orbit types for scientific experiments?
LEO,MEO & GEO with small inclination
48
What are the best orbit types for military satellite missions?
Polar LEO for global coverage, but this can vary
49
What are the best orbit types for testing new technologies?
Various depending on the tech
50
What is the best orbit type for space stations?
LEO (below van-Allen radiation belts)
51
What is the best orbit type for amateur radio satellites?
LEO, but this isn't strict. Typically with small satellites.
52
Describe Geocentric equatorial inertial (GEI) coordinates
GEI coordinates are an inertial reference frame centered on Earth with the equatorial plane as its fundamental plane. Used to describe satellite orbits without accounting for Earth's rotation
53
List of the parameters which are necessary to determine special position of a satellite in the Cartesian Geographic coordinate system (CGeo)
semi major axis (a), eccentricity (e) , time after passage through periapsis (t-tp), longitude of ascending node (Ω), inclination (i), argument of periapsis (ω), sidereal time (ST)
54
Explain the meaning of true anomaly (θ)
Angle between the line of apsides (directed to perigee) and direction to the satellite
55
Describe the meaning of eccentric anomaly (E)
Angle used in Kepler's equation to relate mean anomaly and true anomaly.
56
Describe the meaning of mean anomaly (through its equation)
M=n(t-tp)
57
Describe the meaning of mean motion
Average angular velocity of the satellite (radians per second).
58
Write down an equation which links true anomaly, eccentric anomaly, mean anomaly and mean motion.
sqrt(μ/ a^3) × (t-tp) = E - e×sin(E)
59
Explain line of nodes
The line formed where the orbital plane intersects the equatorial plane
60
explain the meaning of the ascending node and what the right ascension of this node is (RAAN)
The ascending node is the point at which the satellite intersects the equator, moving from south to north.
61
explain what inclination angle is
Angle between the orbit plane and equatorial plane
62
explain what argument of periapsis is.
angle between the ascending node and periapsis
63
explain the difference between a solar day and a sidereal day
A solar day = 24hrs; A sidereal day = 23hrs, 56 mins, 04 secs
64
describe which forces should be balanced in a Lagrange point in a rotating configuration
gravitational & centrifugal forces
65
Describe how earths oblateness disturbs satellite orbit motion and explain why 63.4 degrees inclination is most appropriate for high elliptic orbits
The Earth's equatorial bulge creates perturbing forces. This causes precession of the satellite's orbit (changes in RAAN and argument of periapsis).
At this angle, perturbations from oblateness cancel out, stabilisng the orbit for long-duration missions
66
describe factors which can disturb satellite orbits when considering two body motion, Which factors dominate at different altitudes?
1. Earths oblateness
2. Atmospheric drag (low altitudes)
3. Moons gravitational field
4. Suns gravitational field
5. Suns radiation pressure
67
What equation defines energy consumption rate (Wdot) of a satellite in terms of thrust (F) and exhaust velocity (Ve)?
Wdot= 0.5×F×Ve
68
What equation defines mass consumption rate (mdot) of a satellite in terms of thrust (F) and exhaust velocity (Ve)?
mdot=F/Ve
69
Explain the term specific impulse. Why is it an important characteristic for a thruster.
measures the efficiency of a thruster. It represents the thrust generated per unit of propellant consumed per second
70
What units is specific impulse measured in?
seconds
71
Describe the design of a cold gas thruster
High pressure gas stored in a reservoir is released through a nozzle at high velocities. Consists of a reservoir, filter, pressure regulator, valve, reaction catalyst and nozzle
72
Describe the design and operation of the Electrostatic (gridded ion) thruster.
Neutral gasses collide with electrons (accelerated through the anode and electric fields), creating positively charged ions which are expulsed to produce thrust.
73
What is the advantage of the hall effect thruster when compared to the gridded ion thruster?
No grid corrosion, higher thrust density and simpler design
74
What is meant by the attitude of a satellite?
orientation of a satellite in space relative to a reference frame (e.g., Earth, stars, or its orbit). It is described using angular parameters such as roll, pitch, and yaw.
75
Describe the main attitude control functions
Stabilisation function -To compensate for the effects of disturbance torques. Steering function- A constant bias required to fulfil mission / orbit requirements e.g. Molniya orbit
76
When is a steering function essential for attitude control?
When a satellite requires its attitude to be always pointing towards a certain object, or when a sudden change in orbit/attitude is required.
77
Describe methods of measuring the attitude of a satellite
Reference sensors: Sun sensors, Earth sensors, star sensors, radio frequency sensors, GPS, laser detectors, magnetometers
Inertial sensors: orbital gyrocompasses or laser ring gyroscopes
78
List different types of disturbance torques acting on a satellite
Gravitational torques, solar radiation pressure, magnetic fields, atmospheric drag, lack of thruster alignment with center of mass, impact by meteroid/debris, EM radiation, and outgas
79
Explain what is meant by the principle axis of a body.
An orientation of the bodies reference frame where the sateliite products of inertia, Ixy, Iyz and Izx all = 0.
80
Explain the principle of three-axis stabilisation of satellite attitude.
Three Axes Stabilisation refers to an attitude control system in which the body of the satellite maintains a fixed orientation with respect to the local coordinate system. Consider a satellite with on-board angular momentum (one wheel) aligned in the pitch direction.
81
Explain how Gyroscopic stabilisation is used to limit the motion of a satellite about the pitch, roll and yaw axes. What is the direction of the correcting torque for roll and yaw control?
Pitch control is released by exchanging angular momentum between the wheel and the body of the vehicle (i.e. by varying the rotation rate of the wheel). Roll and Yaw control is obtained by using an actuator which generates a torque about the proper axis
82
Describe methods of passive attitude control and their advantages and disadvantages
Gravity, satellite spin and gyroscopes.
Advantages: No propellant used, no complex equipment
Disadvantages: Small accuracy, large evolution time
83
negatives to methods of active attitude control
uses more propellant, requires complex equipment, equipment has a definite lifespan
84
advantages of methods of active attitude control
Small evolution time, larger accuracies.
85
Describe the types of Angular Momentum Devices as Attitude Control Actuators
Reaction wheels - Non spinning device used for very small constant rotations
Momentum wheels - High rotation speed
Control momentum gyroscope- consists of spinning rotor and motorized gimbals which tilt angular momentum
86
Describe the three main elements of the spacecraft electric power system and the main functions of each element
1. Primary sources - produce electrical energy from other sources (eg solar, nuclear etc)
2. Secondary sources - Substitute for primary sources when they cannot fulfil their function e.g in eclipse
3. Regulation / distribution/protection circuits
87
List the types of primary energy sources used in a satellite
Solar arrays, fuel cells (short missions), batteries, radioisotope thermoelectric generators (RTGs), Nuclear fission reactors (usually military purposes), solar heat system (higher efficiency than solar cell arrays)
88
Describe design of Radioisotope thermoelectric generator (RTG), its advantages and disadvantages. In which mission it is preferable power source?
An RTG relies on the heat produced by decaying radioactive isotopes producing electrical energy via the Seeback effect (in thermocouples).
Advantages - Long term energy, reliable
Disadvantages- Radioactive, careful handling procedures, political concerns
Preferred for far space missions
89
List the types of secondary electric power sources used in a satellite.
Rechargeable batteries, Regenerative fuel cells
90
Describe the Spectral radiance of a black body and a real body. How is the integral emittance of a real body defined?
The spectral radiance of a black body, 𝐿 real = power emitted per unit area of the body, per unit solid angle, per unit frequency.
A real body is a non-idealised black body, with a reduced spectral radiance for the same wavelength. Integral emittance = L real / L black
91
Explain why the absorptance a in the term for the planetary radiation absorption is equal to emittance in the term for heat radiated by a satellite into the deep space.
For a body in thermal equilibrium, Kirchhoff's Law of Thermal Radiation states: α=ϵ.
This equality holds because a body must emit as much radiation as it absorbs when in equilibrium. In satellite terms, absorptance for planetary radiation equals the emittance for radiating heat to deep space to maintain energy balance.
92
Describe the 2nd Kirchoff's law and explain we the integral absorptance of a body does not equal the integral emittance of the radiated body in general case.
Second kirchoffs law states α=ϵ at the same wavelength.
As the EM radiation is emitted and absorbed by different bodies, these can have different temperatures hence this law doesn't necessarily apply.
93
Explain the "visibility factor" for calculation of the albedo radiation.
Visibility factor, based on altitude and attitude angle, is a factor which accounts for earths atmosphere reducing the amount of radiation hitting the satellite body.
94
Describe methods of passive and active thermal control of a satellite.
Passive:
Surface finishes, Insulation, Conducting paths, Phase change materials, Heat pipes
Active:
Heaters, Variable conductance heat pipes and diodes, liquid loops central heating, MPTL, coolers/cryocoolers, heat pumps, louvres & shutters, liquid droplet radiators, ablation
95
Describe design and operation of the heat pipe. How it can be used in the satellite?
Sealed tube filled with a working fluid moving the fluid between an evaporator and condenser, transferring heat along the way. Removes heat from electronic components
96
Describe design and operation of the heat pipe diode. How it can be used in the satellite?
Heat pipe diode ensures heat flow only occurs in one direction, and is used to prevent reverse heat flow between components
97
Describe design and operation of variable conductance heat pipes. How they can be used in the satellite?
VCHPs use a non condensable gas which can block part of the working fluid from condensing. This changes the amount of heat the working fluid deposits, hence varying the conductance of heat. They can be used to regulate the temperature of many onboard systems
98
Describe the reason to cool some sensors and devices mounted on satellite down to temperature close to absolute zero. Which factor restricts the lifetime such satellite to operate?
To reduce signal to noise ratio, Equipment failure often attributes to satellites lifetime being restricted
99
Explain the purpose of the following subsystems: (i) Space segment,(ii) Ground segment, (iii) Control segment operating in space (communication systems)
The space segment contains one or several active and spare satellites organised into a constellation.
• The control segment consists of all ground facilities for the control and monitoring of the satellites, also named TTC (tracking, telemetry and command) stations, and for the management of the traffic and the associated resources on-board the satellite.
• The ground segment consists of all the traffic earth stations. Depending on the type of service considered, these stations can be of different size, from a few centimetres to tens of metres.
100
Describe functions of the Telemetry, Tracing and Command (TTC) block.
1.) Gathering and processing data ready for transmission (Downlink)
2.) Processing and routing commands from ground station for uplink reception
3.) Transponder for satellite ranging
4.) Support services for satellite payload
101
In a satellite communication system describe what is meant by the terms downlink and uplink transmission?
Downlink is providing data to the ground control team from the satellite,
Uplink is giving commands to the satellite.
102
What does effective isotropic radiated power of an antenna mean?
Power of an isotropic antenna radiating the same radiant intensity Φ in all directions as the directed antenna in direction 𝜃.
103
What does free space propagation path loss mean for satellite communications?
Free-space path loss, 𝐿𝐹𝑆, is the loss in signal strength of an EM wave that would result from a line-of-sight path through free space, with no obstacles nearby to cause reflection or diffraction.
104
Explain the term 'Avionics' for a spacecraft or satellite.
Electronic part of Attitude and Orbit Control System (AOCS), but sometimes is used to cover all platform electronics hardware and software: AOCS, TM/TC, data (but does not include payload electronics).
105
List all on-board data handling (OBDH) functions.
1.) Enabling flow of housekeeping and science data
2.) Receiving and distribution commands
3.) Performing telemetry and telecommand protocols
4.) Time distribution around the spacecraft
5.) Providing data storage
6.) Executing command and schedules
7.) Controlling payload and subsystems
8.) Monitoring spacecraft health
9.) Making autonomous decisions
10.) Performing data compressions.
106
Describe the basic forms of on-board data and how they are handling and prepared for transmission.
Signals to be transmitted by a communication system normally consist of a band of frequencies (up to tens kHz for speech and up to tens MHz for TV) which are too low for direct transmission as radio waves. Therefore, the signal is imposed on a carrier wave of much higher frequency suitable for transmission. This process is called modulation.
107
Why does the telemetry signal have to be modulated for transmission to the earth?
Efficient transmission over long distances, multiple signal transmission, compatibility with antennas, noise resistance and better signal processing at the receiver.
108
What are main types of modulations?
1.) Amplitude modulation - AM
2.) Frequency modulation - FM
3.) Phase modulation - PM.
109
Describe all types of modulation of a digital signal.
(Draw diagrams in exam)
1.) Amplitude shift keying - ASK
2.) Frequency phase shifting - FSK
3.) Phase reverse keying - PRK
4.) Quadrature phase shift keying - QPSK.
110
Describe the process of converting of an analogue signal to the digital form.
1.) Sampling
2.) Quantization
3.) Encoding.
111
How is the Nyquist Shannon sampling theorem applied for manipulation with a signal in satellite communication?
It is used within acoustic noise spectrum processing.
112
How can the bandwidth of a signal be defined?
Difference of the highest and lowest frequencies which must be accounted for transmitting a given signal.
113
What are the advantages of digital form of a signal compared to analogue one?
Digital signal can be compressed to have a lower bandwidth than analogue signals. Its relatively noise immune and can be encoded too.
114
Describe what multiply access means.
The ability for a system to serve multiple users simultaneously.
115
Explain the term: transmitting bit error (BER). Why in uplink should BER be essentially smaller than the downlink BER?
Transmitting BER measures the error rate in data transmission and reflects the quality of the communication link.
Uplink BER < downlink BER to ensure reliable satellite operation, as errors in uplink commands can critically impair the satellite, and satellites lack robust error-correction capabilities. Downlink errors are easier to handle with ground station resources.
116
Describe methods for tracking satellite's distance (ranging).
1.) Using GPS or similar navigation system (via trilateration)
2.) Using a TC/TM sub-carrier (involves firing a sinusoidal wave of fixed frequency to the satellite and computing the phase shift between transmitted and received waves).
117
Describe types of antennas employed in satellite communications.
1.) Horn antenna - small aperture & wide beam,
2.) Helical antenna
3.) Parabolic/reflector antenna (best for narrow beam)
4.) Phased array antenna (uses multiple elements to send multiple beams).
118
Describe design and performance of the phase array antenna. What are the advantages of this type of antenna?
Phased array antennas use multiple antenna elements and use wave superposition to build a signal to be transmitted. Has advantages of being able to produce several beams simultaneously.
119
What does antenna gain mean?
describes how much power is
transmitted in the direction of peak
radiation
Boresight antenna gain refers to the maximum gain of an antenna in the direction of its main axis of symmetry, known as the boresight direction. This is the direction where the antenna radiates or receives energy most effectively.
120
What does antenna beamwidth mean?
The angle between the half-power (-3 dB) points of the main lobe.
121
Why is the free-space propagation path loss model used in satellite communications?
The atmosphere can cause reflections/diffractions to occur to satellite signals, reducing the transmitting power over large distances. This needs to be accounted for.
122
Explain the parabolic approximation of the antenna beam.
The parabolic approximation tells us antenna gain is highest when bandwidth is closest to zero. Bandwidth increases causes gain to reduce exponentially.
123
Describe principles of the satellite navigation (GPS).
Satellites send messages to the target. The transmission time is measured, and when combined with satellite positions, target position can be found.
124
Give a list of the sources of errors in position determination by the satellite navigation.
Atmospheric delay, signal multipath, receiver clock error, orbital errors, low number of visible satellites, satellite mutual position, intentional signal degradation.
125
Describe how the conventional and small satellite are classified based on their mass.
Small satellites are less than 500kg. Conventional are 500kg+.
126
Describe the design philosophy for small satellites versus conventional ones.
Conventional sat: Reduced risk -> Increased cost -> Fewer missions
Small sat: Managed risk -> Reduced cost -> More missions.
127
Describe methods of impact protection of satellites.
Whipple bumpers/ shields, act as a wall a small distance from spacecraft exterior. Helps to breakup meteoroids and spread their impact over a larger area.
128
What is the equation for Semi-latus rectum (p), in terms of semi-major axis a and eccentricity e?
p=a(1-e^2).
129
What are the equations for perigee and apogee velocity?
Vp=h/rp and Va=h/ra.
130
What are the equations used to get orbital coordinates, using semi latus rectum, eccentricity and true anomaly theta?
r=p/(1+e×cos(theta)), x=r×cos(theta), y=r×sin(theta).
131
When using inverse tangent, tan-1(y/x), what do you do to your answer when both your terms are positive (aka you're in the top right quadrant)?
Leave as is.
132
When using inverse tangent, tan-1(y/x), what do you do to your answer when x is negative and y is positive (aka you're in the top left quadrant)?
+180 degrees.
133
When using inverse tangent, tan-1(y/x), what do you do to your answer when both x and y are negative (aka you're in the bottom left quadrant)?
+180 degrees.
134
When using inverse tangent, tan-1(y/x), what do you do to your answer when y is negative and x is positive (aka you're in the bottom right quadrant)?
+360 degrees.
135
What's the equation to determine the change in velocity for a change in orbit inclination?
ΔV=2v×sin(Δi/2).
136
What's the equation for frequency of small oscillations?
Ω^2 =3μ/r^3 × (Ix-Iz)/Iy.
137
What's the equation for period of small oscillations?
T=2×Pi/Ω.
138
For a no spin satellite, what's the equation which links time t, change in angle Δθ, moment of inertia I and disturbance torque Td?
t=sqrt(2×I×Δθ / Td).
139
For a spinning satellite, what's the equation which links time t, spin S, change in angle Δθ, moment of inertia I and disturbance torque Td?
t=Δθ×I×S/Td.
140
What is the equation to calculate t1 in pitch control for a flywheel-thruster satellite?
t1=ΔH/Td.
141
What is the equation to calculate uploading time (tu) in pitch control for a flywheel-thruster satellite?
tu=t1×Td/T.
142
What is the equation to calculate T in pitch control for a flywheel-thruster satellite?
T=2×F×L.
143
What is the equation to calculate wx (or wz) in roll (or yaw) control for a flywheel-thruster satellite?
wx=wz=Td/H.
144
What is the equation to calculate t2 (or t3) in roll (or yaw) control for a flywheel-thruster satellite?
t2,3=Δφ/wx,z.
145
What's the equation to calculate correcting time for a flywheel-thruster satellite?
tc=t2,3 × Td/T.
146
What's the shortcut to calculate fuel consumption during an attitude correction on a flywheel thruster satellite?
m=3×Td×t/g0×Isp×L.
147
What's the equation for the power generated by one solar cell (Pc=...)?
Pc=Jsmin×ηEOL×Ac×(1-L)×cos(θ).
148
What's the equation for the energy provided by one chemical battery cell (Ec)?
Ec=Vc × C × ηd × DOD.
149
What's the equation for the mass of a single chemical battery cell (Mc)?
Mc= (C × Vd) / (E/M).
150
What's the equation for albedo radiation Ja?
Ja=Js × a × F.
151
What's the equation for planetary radiation Jp?
Jp=237×(Re / Re+h) ^2 (w/m^2).
152
What's the high level satellite heat balance equation?
Qs+Qa+Qp+Qi=Qsat
Heat from sun + Planetary albedo heat +Planetary radiation heat + Internal heat= heat radiated by satellite.
153
What's the equation for heat received from the sun (Qs)?
Qs= As × α × Js.
154
What's the equation for heat received from planetary albedo (Qa)?
Qa=Aa × α × Js × a × F, where Js × a × F=Ja.
155
What's the equation for heat received from planetary radiation (Qp)?
Qp=Ap × ε × Jp, where ε is satellite emittance value and Jp is planetary radiation, calculated separately.
156
What's the equation for heat radiated by the satellite? (Qsat)
Qsat=Asat × ε ×δ × T^4, where ε is satellite emittance value, and δ is the Stefan Boltzmann constant.
157
Recall the full heat balance equation, combining each of the constituent parts.
(As × α × Js) + (Aa × α × Js × a × F) + (Ap × ε × Jp) +Qi = Asat × ε ×δ × T^4.
158
What's the equation to calculate the fraction of time (fr) the satellite is in the sun, knowing orbit altitude h and earth's radius Re?
fr= 1 - (arcsin(Re/Re+h)/180).
159
What is the Nyquist -Shannon sampling Theorem?
Sampling frequency must be greater than twice the frequency of the input signal. Fs>=2×Fm.
160
How do you calculate wavelength from frequency?
Wavelength = Speed of light / Frequency.
161
What's the equation used to calculate the received power (Pr) from an antenna signal, in terms of power transmitted (Pt), free path loss (LFS), transmitting and receiving gain (Gt & Gr)?
Pr = Pt × Gt × Gr / LFS.
162
When satellites must maintain attitude direction by a certain accuracy (θ) in degrees, the minimum power they receive decreases. Min power = Power received× factor. What equation is used to calculate this factor?
factor = 10^[-1.2×(θ/θ3dB)^2].
163
1 picowatt is equivalent to how many watts?
1×10^-12.
164
What equation would you use to calculate the radius of area on earth's surface covered by a signal radiated from a satellite at distance d, knowing θ3dB of the satellite in radians?
r=d×tan(θ3dB/2).
165
How do you calculate the noise power (N) of a signal, given its temperature T and bandwidth B?
N=kB × B × T, where kB is Boltzmann's constant.
166
What C/N ratio is required for adequate system performance?
C/N >10.
167
What's the equation to calculate maximum bit rate (Rmax) using bandwidth B and C/N Ratio?
Rmax= B × logbase2[ 1+ (C/N) ].
168
How do you calculate the area of a solar sail producing F newtons of thrust, given solar irradiance J and speed of light c?
A = Force / Pressure = (F×c) / (2×J).
