astronomy

Starlette and Stella

Starlette and Stella is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Starlette and Stella rather than just read about it. In short: Starlette (Satellite de taille adaptée avec réflecteurs laser pour les études de la terre, or lit. 'Satellite of suitable size with laser reflectors for studies of the earth') and Stella are nearly identical French geodetic and geophysical satellites. Starlette was launched on 6 February 1975 and Stella on 26 September 1993.

Key takeaways

Starlette and Stella belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Starlette and Stella to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Starlette and Stella from memory before moving on to harder problems.

Reference excerpt

Starlette (Satellite de taille adaptée avec réflecteurs laser pour les études de la terre, or lit. 'Satellite of suitable size with laser reflectors for studies of the earth') and Stella are nearly identical French geodetic and geophysical satellites. Starlette was launched on 6 February 1975 and Stella on 26 September 1993. Starlette was the first passive laser satellite developed.

Background Starlette's development dates back to at least 1972, when scientists at the Centre national d'études spatiales (CNES) were trying to determine a payload for the upcoming first flight of the new Diamant BP4 rocket. After consulting with the Smithsonian Astrophysical Observatory, CNES scientists decided to create a small geodetic satellite optimized for tracking by laser ranging. The project was approved within a few months after a feasibility study by the French atomic agency CEA determined the dense uranium core could be made nearly non-radioactive by using depleted uranium. The Groupe de recherches en géodésie spatiale (GRGS; Space Geodesy Research Group) first proposed Stella to provide coverage for areas missed by Starlette.

Spacecraft design Starlette and Stella are nearly identical, small spherical spacecraft measuring 24 centimetres (9.4 in) in diameter. With masses of 47 kilograms (104 lb) and 48 kilograms (106 lb) respectively, the satellites are quite dense. This high-density spherical design reduced the drag effect of aerobraking on the satellites as they exited Earth's atmosphere. Both satellites are covered in 60 laser retroreflectors.

Mission and results Starlette was launched on 6 February 1975 at 16:35 UTC by a Diamant BP4 rocket from the B launch pad at the Guiana Space Centre in Korou, French Guiana. It was the first flight of a Diamant BP4 launch vehicle. Stella was launched on 26 September 1993 at 01:45:00 UTC by an Ariane 4 (Ariane 40 H-10) rocket from the ELA-2 launch pad at the Guiana Space Centre as part of a payload also containing the satellites SPOT-3, KITSAT-2, Itamsat, Eyesat-1, PoSAT-1, and Healthsat-2. The payload was located in the top part of the Ariane rocket's third stage. In the 1980s, data gathered by Starlette was used to develop a model of global ocean tides.

Legacy and status Starlette was the first passive laser satellite developed. The first of two American geodetic satellites called LAGEOS followed not long after in 1976. Both satellites were in orbit as of 2023. They are expected to remain in orbit up to 2000 years and to remain trackable for many decades or centuries.

Illustrations

Worked examples

Example 1 — a first encounter with Starlette and Stella

Start with the simplest possible case. Write down what Starlette and Stella claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Starlette and Stella before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Starlette and Stella ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Starlette and Stella

In research: Starlette and Stella appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Starlette and Stella in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Starlette and Stella is common in secondary-school and first-year university syllabi. It links to neighbouring topics Laser ranging satellites, Satellites of France, Satellites orbiting Earth, so understanding it makes those chapters shorter.
In everyday life: Look for Starlette and Stella outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Starlette and Stella in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Starlette and Stella means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Starlette and Stella out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Starlette and Stella in simple terms?

Why does Starlette and Stella matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Starlette and Stella?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Starlette and Stella.