Lunar and cislunar missions are forms of space journeys. Lunar missions refer to those that land on the moon's surface, while cislunar missions refer to spacecraft traveling in the space between Earth and the moon. Cislunar is Latin for "on this side of the moon;" however, there is not a commonly accepted definition of cislunar space across the international or technical community. Competing definitions include the following:
- The space between the Earth and the moon, including the moon's orbit, low Earth orbit (LEO), medium Earth orbit (MEO), and geosynchronous orbit (GEO)
- The space between GEO and the moon's surface
The lack of a consensus is likely due to there being no clear point or distance from Earth at which the properties of the environment change significantly to separate it as cislunar space.
Lunar and cislunar missions date back to the 1950s and the space race between the United States and the Soviet Union. While the Soviet Union had many firsts, including launching the first artificial satellite (Sputnik, 1957) and the first spacecraft to reach the moon (Luna 1, 1959), the United States became the first, and currently only, country to land humans on the moon. On July 20, 1969, the Apollo 11 mission landed US astronauts Neil Armstrong and Edwin “Buzz” Aldrin on the Lunar surface.
Various companies perform business operations, missions, and more in cislunar space, and many are making strides to land rovers and humans on the lunar surface for further space exploration and scientific discovery. Government efforts can enable or utilize private industry missions, or in some instances, commercial space companies are independently pursuing their own missions. Many nations view lunar and cislunar investment as a way of advancing their domestic space industry and as the initial step towards greater presence in near-Earth space. They are also driven by the scientific and economic factors of having a space presence and building international partnerships. Lunar and cislunar missions have the potential for celestial resource extraction and in situ resource utilization (ISRU) or the production and manufacture of materials found on the moon and other celestial bodies.
There are also military reasons for pursuing lunar and cislunar missions, and a growing number of countries are pursuing military uses in space. Specific locations in cislunar space and on the moon hold important strategic value. This includes locations with specific physical properties, such as orbital stability or the potential for more beneficial resources. With the signing of the 2020 National Defense Authorization Act, the US government committed to funding the US Space Force (USSF), its first new military service in over seventy years. The USSF is responsible for "organizing training, and equipping Guardians to conduct global space operations that enhance the way our joint and coalition forces fight, while also offering decision-makers military options to achieve national objectives." Other nations pursuing military applications in space include India (performed an anti-satellite weapons test), Iran (launched military satellites), China (established the Strategic Support Force to handle the fields of space, cyber, and the electromagnetic spectrum), Russia (set up an independent Space Force), and France (established the Space Command).
Lunar exploration includes any mission aiming to land on the moon's surface; this could include crewed or uncrewed missions with either a lander or rover component. The Soviet Union was the first nation to perform a successful soft landing on the moon with the Luna 9 mission in early 1966. This was followed four months later by NASA's Surveyor 1 mission, successfully landing on the lunar surface on June 2, 1966. While other countries and the European Space Agency (ESA) have performed hard landings on the moon, only China has successfully joined the United States and the Soviet Union/Russia in performing a successful soft landing. In December 2013, China's Chang'e 3 lander touched down, the first lunar landing since the Soviet Union's Luna 24 mission in 1976. China's Chang'e 4 completed the first soft landing on the dark side of the moon in 2019. The Yutu-2 rover, part of the Chang'e 4 mission, is the only operational rover on the moon. Data from China's Lunar Exploration Ground Application System in September 2022, showed the solar-powered rover has traveled 1,029 meters (3,376 feet) across the Von Kármán crater.
Stitched panoramic image from the Yutu-2 rover.
Multiple other countries with active space programs or privately funded space programs have stated their intention for crewed or uncrewed soft landings on the moon by 2030. These include:
- Canada—possible autonomous impactor mission as well as a joint mission with the EU and Japan
- European Union—possible joint lander and sample-return mission alongside Japan and Canada, possible solo rover mission
- India—following the high-speed touchdown of Chandrayaan-1 and the failed soft landing of Chandrayaan-2, India will again attempt a successful soft landing with Chandrayaan-3
- Israel—Israel-based SpaceIL's Beresheet moon lander reached the moon in February 2019 but crashed during landing. Follow-up attempts are planned.
- Japan—Japanese Aerospace Exploration Agency (JAXA) is planning a crewed landing; privately held company ispace is working with the US and UAE on lander-focused missions.
- Mexico—sending micro rover as payload on a future US/Mexico joint mission
- South Africa—planned lander and rover mission could launch in 2030
- South Korea—planned lander and rover mission could launch in 2030
- Turkey—planned hard and soft landing missions by the end of the decade
- Ukraine—working alongside collaborators in UK and US to conduct a mission to explore lunar caves. The conflict with Russia will likely delay the mission.
- United Arab Emirates—companies based in UAE, Japan, and the US are working together on an upcoming mission in which a SpaceX Falcon 9 rocket will carry a Japanese-designed lander and the UAE's lunar rover.
- United Kingdom—working alongside Ukrainian and USA-based companies to conduct a mission to explore lunar caves, also planning a solo sample retrieval mission.
NASA's Artemis Program is a series of missions to land the first woman and first person of color on the moon. The program is a collaboration with commercial and international partners and is looking to establish the first long-term presence on the moon, including building the Artemis Base Camp on the lunar surface and the Gateway in lunar orbit.
Cislunar travel and exploration refer to travel or explorations occurring in the spaces between the Earth and the moon. Cislunar travel is becoming more popularized by the private and public sectors due to the rising demand to commercialize space travel. The commercialization of space travel is aimed at making low-orbit space a premier destination for vacationing, cargo transport, and expanding in space-capable technologies. Pushing for commercialization allows private companies to develop technologies that further deep-space exploration while creating economies in low-orbit for the general public. NASA states that turning over low-orbit travel to the private industry allows federally-funded space programs to focus on the larger goal of landing humans on Mars.
Cislunar space includes the five Lagrangian points that offer stable orbits in reference to the Earth and moon. For example, the James Webb Space Telescope launched on December 25th, 2021, orbits the sun at the second Lagrange point (L2), allowing it to stay in line with the Earth as it moves around the sun. The first and second Lagrange points, L1 always in front of the moon and L2 always behind the moon, offer benefits for transport purposes. Vehicles visiting a future space station placed at L1 and L2 do not require reentry shells or landing legs. Even large objects can be kept at Lagrange points with minimal propellant.
On November 17, 2022, the White House Office of Science and Technology Policy released the US's first National Cislunar Science and Technology (S&T) Strategy to address how to "support responsible, peaceful, and sustainable exploration and use of Cislunar space... by all space-faring nations and entities, consistent with the U.S. Space Priorities Framework." NASA estimates 2022-2032 will see human activity in cislunar space that will equal or exceed all previous human activity from 1957 to 2022. The National Strategy includes four key science and technology objectives:
- Supporting research and development to enable future growth in cislunar space. R&D opportunities in cislunar space range from novel discoveries in space science to the development of new Cislunar technologies and new breakthroughs in understanding the effects of the space environment on humans.
- Expanding international cooperation in cislunar space.
- Extending U.S. space situational awareness capabilities into cislunar space, including early warning systems for potentially hazardous asteroids.
- Implementing cislunar communications and positioning, navigation, and timing capabilities with scalable and interoperable approaches.
Cislunar space has the potential to advance science, technology, and exploration. Applications include:
- Utilizing the unique characteristics of space (microgravity, vacuum, high-intensity solar exposure, isolation from Earth, etc.) to produce useful knowledge and products
- Harvesting and processing material and resources from celestial bodies
- Building more sophisticated structures in Earth and lunar orbit
- Supplying future installations on the moon
- Utilizing radio-quiet environments for a new generation of radio astronomy
The International Space station was launched on November 20, 1998. Owned by federal governments, it has remained in orbit since its initial launch. It is consistently crewed by astronauts and is never left unattended. Five government space organizations are responsible for the International Space Station operations:
- NASA (United States)
- Roscosmos (Russia)
- CSA (Canada)
- JAXA (Japan)
- ESA (European Space Agency member countries)
The China National Space Administration first launched a space station, Tiangong-1, into Earth orbit in September 2011, which hosted astronauts twice in 2012 and 2013. It was put into sleep mode in 2013. In September 2016, China launched its successor, Tiangong-2, which hosted two astronauts for thirty days after launching. In 2018, they announced Tiangong-2 would eventually de-orbit in a controlled destruction. This occurred on July 19, 2019, with the spacecraft disintegrating over the Pacific Ocean. The two previous space stations paved the way for a permanent Tiangong space station, the first module of which, named Tianhe, launched on April 29, 2021. This was followed by two experiment modules launched on July 24, 2022, and October 31, 2022.
In 2019, NASA selected various companies to join a study called the Space Relay Partnership and Services as a part of the Space Communication and Navigation (SCaN) program. The study was developed to establish public-private relationships with United States commercial communications companies to further NASA’s existing communications technology network.
Surveillance of space is necessary because of the vast amount of satellites and other artificial debris that is orbiting the Earth. Inactive satellites need monitoring to ensure they don’t collide with functional satellites, unexpectedly reenter the atmosphere, prevent returning objects from being identified as missiles, and more. Surveillance of space objects is primarily conducted by the United States Air Force, the United States Space Force, and its private-public partnerships with other companies. Many private companies also monitor space objects in an effort to collect, market, and sell space data to the U.S. government.
