The exploration of Venus has indeed seen fewer successful lander missions compared to other celestial bodies in our solar system. There are several reasons for this disparity:
Harsh Surface Conditions: Venus has an extremely hostile environment. The surface temperature averages around 450 degrees Celsius (842 degrees Fahrenheit), which is hotter than the surface of Mercury, despite Venus being farther from the Sun. The atmospheric pressure on Venus is about 92 times that of Earth, equivalent to being almost 1,000 meters (3,280 feet) deep underwater. The combination of high temperature and pressure, along with a corrosive atmosphere consisting mainly of carbon dioxide, makes it extremely challenging for landers to survive on the surface of Venus for an extended period.
Technical Challenges: Designing a lander capable of withstanding the extreme conditions on Venus is highly complex. The materials used in spacecraft construction, as well as the electronics and other systems, need to be able to endure the intense heat and pressure. Developing such robust and resilient technologies is a significant engineering challenge.
Limited Operational Lifetime: The harsh conditions on Venus also significantly limit the operational lifetime of landers. The extreme temperatures and high atmospheric pressure can quickly degrade the lander's instruments and systems. Additionally, the acidic nature of the Venusian atmosphere can corrode and damage the spacecraft's components over time.
Scientific Priorities and Cost: Exploration missions are often guided by scientific priorities and cost considerations. Funding agencies and scientific communities decide which missions to prioritize based on scientific objectives, available resources, and the potential for groundbreaking discoveries. These factors influence the selection of mission concepts and the allocation of resources for exploration efforts.
Despite the challenges, there have been successful lander missions to Venus in the past, including the Soviet Union's Venera and Vega programs, which deployed a series of landers and balloons in the 1970s and 1980s. More recently, NASA's Parker Solar Probe, while primarily focused on studying the Sun, has also conducted Venus flybys to gather valuable data about the planet.
As for the lack of an orbiter dedicated solely to Venus, it could be due to a combination of factors such as funding constraints, mission prioritization, and the focus on other celestial bodies that may be deemed higher priorities at a given time. However, various proposals and concepts for Venus orbiters have been suggested, and future missions might be planned to explore and study Venus more comprehensively.