Why is the Mars Insight Lander Launched from Vandenberg Air Force Base?
The Mars Insight Lander was launched from Vandenberg Air Force Base instead of the more traditional Kennedy Space Center near Cape Canaveral in Florida. This decision is rooted in the logistics and scientific requirements of the mission. Let's explore the reasons behind this unique choice.
Logistical and Operational Reasons
Logistically, the choice of launch site is driven by two primary factors: availability and cost. Vandenberg Air Force Base had more available time slots during the Insight mission's launch window, making it a more practical option compared to the congested schedule at Kennedy Space Center (KSC).
In a tweet, Caley Burke, a trajectory analyst for NASA's Launch Services Program, explained that the Atlas V-401 rocket used for the Insight mission had sufficient excess performance margin to allow for a launch from Vandenberg AFB, providing the needed flexibility to spare KSC congestion.
Science and Trajectory Considerations
Scientifically, the decision to launch from Vandenberg Air Force Base aligns with the mission's trajectory requirements.
Mark Wallace, the designer of Insight's trajectory, provided a detailed explanation of the physics involved in deciding the launch site. Earth rotates at approximately 30 km/s, and the Atlas V rocket can add a few additional km/s to its velocity in a specific direction. This additional velocity is crucial for targeting the correct landing site on Mars. The key parameter to consider is the declination angle (DLA), which is affected by both Earth's rotation and its tilt.
A launch from Cape Canaveral can achieve a DLA within ±28.5 degrees, which is ideal for missions departing from the east coast. However, a launch from Vandenberg AFB, while sacrificing some of this eastward momentum, still provides a viable trajectory to Mars due to the Atlas V's excess performance margin. As Burke noted, 'launching the InSight mass to the 2016/2018 Mars targets for its landing site had enough excess performance margin on the Atlas V that both coasts could be utilized.'
Wallace further explained that the park orbit inclination needs to be less than the DLA for efficient escape into the correct trajectory. A polar orbit can achieve this by aligning the launch velocity vector, which can point either "up" or "down" as the spacecraft transitions from the equator to the poles.
Balancing East and West Coast Options
Although launching from Florida is traditionally more efficient for planetary missions due to the eastward momentum provided by Earth's rotation, the Atlas V's power allowed for alternative launch site choices. When the mission was originally scheduled for 2016, the east coast launch schedule was busy, and Vandenberg AFB was chosen as a viable option. The decision to keep this site even after the mission was delayed to 2018 was driven by the Atlas V's performance capabilities and the availability of launch slots.
Conclusion
The decision to launch the Mars Insight Lander from Vandenberg Air Force Base reflects a strategic balance between logistical and scientific requirements. While the traditional Kennedy Space Center offers the benefits of launching towards the east, the flexibility provided by Vandenberg AFB, combined with the Atlas V's performance margin, made this site a practical choice for the Insight mission.
Future missions may continue to explore the balance between these factors, potentially influencing the choice of launch sites for interplanetary missions.