Self-Assessment Quiz: Small Satellites, CubeSats, and Constellations

Twenty-two questions to check your grasp of the democratization of space, the CubeSat standard, small-sat subsystems, rideshare, constellations, and the debris question. Answer each before opening the key. Aim for 17 or more.

Question 1

The two cost collapses that together democratized access to space were:

A) cheaper rocket fuel and cheaper metals B) cheaper, more capable electronics and cheaper launch C) faster computers and much larger rockets D) government subsidies and international treaties

Question 2

"COTS" stands for:

A) Cheap Orbital Test Satellite B) Commercial Off-The-Shelf C) Coordinated Orbital Tracking System D) Common Orbital Transfer Stage

Question 3

The principal cost of using COTS parts instead of space-qualified ones is that they are generally not:

A) available B) affordable C) radiation-hardened or space-qualified D) high-performance

Question 4

A satellite with a launch mass of $40\ \text{kg}$ falls in which class?

A) minisatellite B) microsatellite C) nanosatellite D) picosatellite

Question 5

A "1U" CubeSat is a cube whose side length is:

A) $1\ \text{cm}$ B) $10\ \text{cm}$ C) $30\ \text{cm}$ D) $100\ \text{cm}$

Question 6

The chapter argues that the CubeSat revolution was primarily one of:

A) miniaturization B) standardization C) propulsion D) radiation-hardening

Question 7

The interplanetary CubeSats that relayed the InSight lander's Mars landing were what size?

A) 1U B) 3U C) 6U (MarCO) D) 12U

Question 8

The signature small-sat attitude actuator — no moving parts, minimal power, works by pushing against Earth's magnetic field — is the:

A) reaction wheel B) control moment gyroscope C) magnetorquer D) ion thruster

Question 9

Many CubeSats cannot dodge a collision or deorbit themselves because they lack:

A) an onboard computer B) a radio C) propulsion D) solar panels

Question 10

On a typical 3U CubeSat, the resource that most limits what the satellite can actually do is usually:

A) internal volume B) orbit-average electrical power (a few watts) C) mass D) data storage

Question 11

Rideshare means:

A) reusing a rocket's first stage B) launching many independent payloads on one rocket and splitting the cost C) several satellites sharing a single orbit D) two crews sharing a capsule

Question 12

A CubeSat deployer such as the P-POD ejects its satellites at a relative velocity of roughly:

A) $0.001\ \text{m/s}$ B) $1$–$2\ \text{m/s}$ C) $50\ \text{m/s}$ D) $500\ \text{m/s}$

Question 13

Compared with a dedicated small launcher, rideshare is far cheaper per kilogram but you give up:

A) reliability B) control over your orbit and launch schedule C) the ability to use COTS parts D) your data rate

Question 14

A constellation achieves continuous coverage from low Earth orbit by:

A) using a single very large satellite B) flying higher than GEO C) flying enough coordinated satellites that one is always in view of each user D) relying only on inter-satellite links

Question 15

If you raise the minimum elevation angle a user requires (the satellite must be higher in the sky), the number of satellites needed for continuous coverage:

A) decreases B) stays the same C) increases D) drops to zero

Question 16

Starlink flies far more satellites than continuous coverage alone requires, chiefly because of:

A) legal quotas B) capacity — the bandwidth demanded by users in a region C) redundancy alone D) launch-vehicle limits

Question 17

The strongest reason to build a broadband service in LEO rather than GEO, despite needing thousands of satellites, is:

A) finer imaging resolution B) much lower signal latency C) cheaper individual satellites D) less radiation exposure

Question 18

A dead satellite at $550\ \text{km}$ re-enters within a few years, while one at $1{,}200\ \text{km}$ persists for centuries, because of the altitude dependence of:

A) solar radiation pressure B) atmospheric drag (air density) C) Earth's magnetic field D) gravity

Question 19

The runaway cascade of collisions that could render an orbital shell unusable — introduced here and developed in Chapter 35 — is called the:

A) Oberth effect B) Kessler syndrome C) Hohmann cascade D) Lagrange instability

Question 20 (True/False, justify)

"Because coverage geometry gives $N_{\min} \approx 184$ satellites at $550\ \text{km}$, a real broadband constellation at that altitude needs about 184 satellites." True or false? Justify in one sentence.

Question 21 (True/False, justify)

"Buying a whole Falcon 9 is always the cheapest way to launch any satellite, because it has the lowest cost per kilogram." True or false? Explain briefly.

Question 22 (Short answer)

State the three coverage-geometry relations of §33.5 (nadir angle, Earth-central angle, footprint fraction) and say, in one sentence, what $N_{\min}$ represents and why the real fleet is larger.

Answer Key

Q Ans Note
1 B Cheap capable electronics (Moore's law) + cheap launch (reuse + rideshare); the two multiply.
2 B Commercial off-the-shelf — bought from a catalog, not custom space-qualified.
3 C COTS parts are not radiation-hardened/space-qualified; reliability is bought back by redundancy, screening, short life, numbers.
4 B Microsatellite = $10$–$100\ \text{kg}$.
5 B $1\ \text{U} = 10\ \text{cm}$ cube (one litre).
6 B A common standard made satellites modular and rideshare-able; small size alone did not.
7 C MarCO-A and MarCO-B were 6U CubeSats.
8 C Magnetorquers: no moving parts, milliwatts, push on Earth's field (useless far from Earth).
9 C No propulsion → cannot maneuver, avoid collisions, or actively deorbit.
10 B Orbit-average power is only a few watts; every subsystem must fit inside it.
11 B Many payloads split one rocket's fixed cost (e.g., Transporter-1's 143 satellites).
12 B A spring ejects at ~$1$–$2\ \text{m/s}$ so payloads drift apart safely.
13 B Rideshare gives you the provider's orbit and date; a dedicated launcher sells control.
14 C Numbers substitute for altitude: enough satellites that one is always overhead.
15 C Higher $\varepsilon$ shrinks $\lambda$ and the footprint, so more satellites are needed.
16 B Thousands are driven by bandwidth/capacity per user, beyond mere coverage.
17 B LEO round-trip latency is milliseconds vs GEO's ~quarter-second — decisive for interactive use.
18 B Drag ∝ air density, which falls steeply with altitude; low orbits self-clean, high ones do not.
19 B The Kessler syndrome (developed in Chapter 35).
20 False $N_{\min}$ is an instantaneous, no-overlap, coverage-only floor; real fleets need 2–3× for overlap and far more for capacity.
21 False Low cost per kg applies only if you fill the rocket; for one small satellite the effective cost per kg is enormous — rideshare wins.
22 — $\sin\eta = \frac{R_E}{R_E+h}\cos\varepsilon$; $\lambda = 90^\circ - \varepsilon - \eta$; $f = \frac{1-\cos\lambda}{2}$. $N_{\min} \approx 1/f$ is the minimum satellites for instantaneous global coverage assuming perfect tiling; real constellations need more for overlap and for capacity.

Topics to review by question

Questions Topic Section
1, 2, 3, 4 Democratization; COTS; mass classes §33.1
5, 6, 7 The CubeSat standard and the unit §33.2
8, 9, 10 Small-sat subsystems (power, ADCS, propulsion) §33.3
11, 12, 13, 21 Rideshare, deployers, cost per kg §33.4
14, 15, 16, 17, 20, 22 Constellations and coverage geometry §33.5
18, 19 Economics and the debris question §33.6