Orbits. (astronomical software) (Software Review) (Evaluation)
by Peter Scisco

Explore heavenly bodies and discover the workings of our closest celestial neighbors in this great introduction to our solar system.

Outer space may be considered the final frontier in the popular imagination, but in the context of the celestial universe, there's nothing final about it. The universe may or may not have enough mass to sustain itself; it may or may not at some point begin a slow collapse into nothingness. What we know about the cosmos is dwarfed by the very subject we study.

Orbits helps amateur cosmologists understand the dynamics of the universe by bringing the final frontier into our own backyard. Rather than casting its eye outward to the stars, Orbits limits its study to the solar system of which our earth is part. This family of planets, circling a medium-sized star, serves as a fine introductory point to the study of astronomy.

The program's design is clean, simple, and easily navigated. Small touches, like using a tiny space shuttle as a cursor, create a feeling of adventure and fun. The promise of adventure makes it easier to approach the complex workings of the solar system and its planets.

In general terms, the program is divided into animated displays that describe the solar system, written explanations, and a series of "games" (orbital simulations and a jigsaw puzzle) that allow the user to experiment with the gravitational laws that control orbits and reconstruct jumbled pictures of space objects.

The descriptive parts of the program are listed at the top of the animated main menu screen. Here, our solar system is divided into its main components: sun, earth, moon, and planets. You can choose to have the screen animated or not. The animation consists of colored bands, or rings, that define the orbits of the planets around the sun and their relative position to each other as seen from a perspective just about the plane of the solar system. The General menu includes such topics as gravity and the motions of planets; it offers a path into the study of orbital mechanics. In addition to selecting from the pull-down menus, users can move the cursor over any of the solar system bodies to gain access to information about a particular planet or celestial body.

If Orbits concerned itself only with pretty pictures and animated display, its usefulness would be short-lived. But the information that accompanies the still pictures and animations is accurate and presented in a manner appealing to beginning astronomers of any age. The program makes use of authoritative sources for both its explanations and its graphic displays. These sources include NASA and the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California.

The blend of graphic displays and explanatory notes is seamless and graceful. For example, if you're interested in the earth's moon, you can explore lunar features, study the moon's internal structure, and compare the moon to other bodies in the solar system. Each of these selections, or paths, branches to more specific areas of study.

A student interested in lunar features could explore maria (the dark plains created by ancient lava flows), craters, rays (bright streaks emanating form craters, believed to be composed of rock and dust thrown up at the time of impact), atmosphere, and such lesser features as lunar mountains and the steep crevasses called rills.

Every planet is covered in the same way, as are asteroids, comets, and the sun. Each discussion includes the subject's distinct characteristics and offers pictures and animations that explain the ideas behind the words.

But, as Einstein might say, all of these voyages of discovery are relative. An eager student may journey into the core of the moon or explore the atmosphere of Jupiter. But what can be made of the facts encountered? Orbits boosts the process of discovery by allowing users to compare planetary descriptions side by side. The juxtaposition of facts and pictures creates a basis of comparison that helps users envision the facts and details that describe the solar system.

A parent using this program with a child, for example, might compare the structure of Mars with the structure of the earth to illustrate the similarities of the two. Or a student studying the earth's moon might compare that body with the earth and discover enough similarities to fuel a school report.

Once you've studied the major planets and other bodies that constitute our solar system, you can begin a journey into the physics and phenomena that play a role in our tiny corner of the galaxy. Detailed and animated explanations for eclipses, phases of the moon, gravitational attraction, and orbital mechanics make it easy to understand the dynamics behind them.

For example, eclipses both lunar and solar are displayed in a split-screen fashion that makes the alignment of the earth, moon, and sun understandable. The top part of the screen is from a perspective outside the earth's orbit; you can see the moon revolving around the earth and how it crosses between the sun and the earth, blocking the light (solar eclipse). At the bottom of the screen, the view is from the earth, looking toward the sun. You can see the shadow of the moon as it passes over the sun and compare that to the position of the moon, sun, and earth as displayed above.

Likewise, the relationship between the sun, moon, and earth as it affects the phases of the moon is made clear through another well-presented bit of animation. Although an astronomy hobbyist could do the same on paper by observing the position of the moon throughout a full cycle and by sketching the moon's phases at separate stages of the cycle, the animated display in Orbits provides more instant recognition.

Orbits provides more than information and tools for understanding; it also includes an extremely challenging orbital simulator. To gain entry to this part of the program, select the Other menu and then select Orbital Mechanics. From here you can brush up on Kepler's Laws (you probably remember all of those) and see the importance of Kepler's mathematical theories to the study of our solar system.

With a clear understanding of orbital mechanics (or with at least a hearty sense of adventure), you can choose to play Orbit-Trek, which tests your knowledge under different conditions. You may select from four different missions: Near Earth, which is a good shakedown cruise for your newly acquired skills; Deploy, which requires that you reach and maintain a specific orbit and then launch a satellite; intercept, which requires that you capture an orbiting satellite; and Rendezvous, which tests your ability to match orbits with a second satellite and fly in formation.

The Orbit-Trek games employ a control panel from which you select the direction and strength of your navigational thrusters. Early experimentation with the game sometimes results in a fifth scenario, which could be called Lost in Space. Just for fun, see how far you can drift from the earth before you reach the point of no return.

With its combination of authoritative explanations and well-designed graphic displays, Orbits is a very good computer-based introduction to our nearest heavenly neighbors. By illustrating the workings of the family of planets we call the solar system, Orbits lays the groundwork for a continuing mission.