Update: Watch my video version of this article.

We've all heard about how NASA launched the James Webb Space Telescope (hereafter JWST) and how it's now in an orbit somewhere beyond the moon. But how do we know the telescope will stay where it's positioned — logically, shouldn't it fall back toward the earth or drift away?

In this article I explain how the telescope's designers planned the space and orbital aspects of this ambitious mission, using prior computer modeling to anticipate issues that might come up. To prepare this article I wrote my own computer model (running at the top of this page) and proved to my own satisfaction that the planned orbit is feasible, although it requires periodic tuning to remain stable.

Here are this article's sections:

• In Section 1 I explain the mathematics and physics of orbits, including some graphic examples — how NASA and others are able to predict what a spacecraft will do once launched.

• In Section 2 I explain how I wrote my orbital model, which computer languages I've tried and how accurately the model imitates nature. This section will be of particular interest to young programmers planning a career, some of whom may be writing code in the wrong language.

• In Section 3 I explain the details of a Lagrange-point orbit, how it works and what its limitations are. This section includes a user-interactive live model with three-dimensional viewing capability.

Readers can navigate this article using the above links and/or with the arrows located at the top and bottom of this page.