A note on dates
This article deliberately names no launch dates or specific missions. Space schedules change often, and anything written here could be out of date by the time you read it. Missions are delayed, redesigned, renamed or canceled for technical, budget and political reasons. For current information, check the official websites of the agency in question, such as NASA or its counterparts in other countries, which keep up-to-date mission pages. What follows explains the kinds of missions that agencies typically plan and why.
How missions get planned
Space missions take years, often a decade or more, from first idea to launch. A common pattern is that the scientific community compiles priorities, sometimes through formal reviews that set out the most important questions for a field. The agency then solicits proposals, often through competitions, selects among them based on science value, cost and technical risk, and funds the chosen ones through design, building, testing and launch.
Budgets matter greatly. Missions are commonly grouped by size and cost, from small, focused projects to large flagship efforts. Smaller missions can be developed more quickly and may take more risk. Flagships can carry many instruments and answer broad questions, but they cost more and take longer, so there are fewer of them.
Lunar missions
The Moon is a frequent target. Reasons include science, such as studying lunar rocks to learn about the early solar system and the history of lunar formation, and preparing for future crewed activity. Lunar missions can take several forms:
- Orbiters that map the surface and measure its composition.
- Landers and rovers that study specific sites, including regions near the poles, where some areas are in near-permanent shadow and may contain ice.
- Crewed missions, which require much more complicated systems for life support, safety and return.
- Technology demonstrations that test equipment for use on later missions.
Planetary and small-body missions
Robotic missions have visited planets, moons, asteroids and comets. Typical mission types include:
- Flybys, which pass a target once, collecting data quickly.
- Orbiters, which stay in orbit for long-term study.
- Landers and rovers, which examine the surface up close. Mars has been a popular target partly because of interest in the Martian climate of the past and whether the planet was ever habitable.
- Sample-return missions, which collect material and bring it back to Earth for study in laboratories that have much more capable instruments than any spacecraft can carry.
- Missions to icy moons, where interest focuses on subsurface oceans that might be habitable.
Planning for such missions depends on orbital mechanics. Launch opportunities to some planets come around only every year or two (roughly every two years for Mars) because of relative positions, which is one reason delays can have large consequences.
Space telescopes and observatories
Telescopes in space avoid the blurring and absorption of the atmosphere, which blocks many wavelengths, including much of the ultraviolet, X-ray and infrared. Space observatories are designed for specific types of light, such as infrared, X-rays or gamma rays, or for particular tasks, like surveying the sky, finding planets around other stars or studying dark energy. They need long development, careful testing before launch, since most cannot be repaired once in space, and often operate at distant locations that offer stable conditions.
Earth science and heliophysics
Not all missions look outward. Agencies also fly satellites to observe Earth’s land, oceans, ice and atmosphere, and others that study the Sun and the space environment, including space weather that can affect satellites and power systems. These missions often receive less public attention but provide data used by researchers and by many practical services.
Human spaceflight and commercial partnerships
Agencies also plan crewed activities in low Earth orbit and beyond. In recent years, many agencies have worked with private companies for launch or cargo services. How roles are divided between public and private organizations changes over time and varies from country to country. Because plans are complicated and evolving, avoid treating any single announcement as final.
How to follow the news sensibly
- Use primary sources. Agency mission pages, press releases and scientific team websites are the best places to learn the current status.
- Expect change. A date described as a target is not a promise. Delays are normal, particularly for complex launches.
- Watch for hype. Be cautious of headlines that claim a mission will “prove” something or a “revolutionary” outcome. Mission results often turn out to be more nuanced and take years to analyze.
- Look at international efforts. Many missions are joint projects, and several agencies around the world run active programs.
Understanding the general pattern, the types, the process and the reasons for delay, makes it easier to read any specific announcement critically and enjoy the process as it unfolds.