What does T minus mean? Learn all about the satellite launch lingo in this guide

The launch of a satellite is definitely considered to be one of the greatest human inventions. First of all, it is a matter of national pride and second, with the launch of a satellite, humans can learn about space in great detail. In this post, we are going to have a closer look at the complete details of the T minus meaning, key terms of a satellite launch, and more.

The complete details of T minus

T minus and L minus are terms that are commonly heard during the launch of any spacecraft. L, pronounced as L minus, refers to the days, hours, and minutes remaining in the scheduled countdown to launch a satellite, which occurs at L0. The L stands for launch. In the same way, T pronounced T minus, refers to the time remaining on the official countdown clock. The T stands for time. During planned stoppages in the countdown process when the countdown clock is intentionally stopped, the T minus time also stops. The L minus time, however, is synced to the clock on the wall and continues to advance forward to the launch time. Under normal conditions, these countdowns remain in sync. For example, there is a 15-minute stoppage planned at T minus 4 minutes, which occurs at L minus 19 minutes. Once the stoppage is lifted and the countdown resumes, the clocks will be synced and show 4 minutes remaining. In the next section, we will have a look at the key terms of a satellite launch.

The key terms of a satellite launch

• Two stages: Two stages mean that the rocket has two sections, or stages, that are mounted on top of each other. Each stage has its own fuel and its own engine. Each stage is ejected into space once its job is done and all the fuel is spent.
• Upper stage: It is considered to be the brain of the satellite. It is designed to power the second leg of the satellite's trip, placing it into a geostationary orbit.
• Liftoff: Liftoff means the exact moment when the rocket, with the satellite onboard, begins to leave the launch pad under its own power, and it starts its journey to space.
• Main engine start and main engine cut-off: Main engine start refers to the moment when the Centaur Upper Stage’s main engine begins to fire, or burn. Main engine cut-off refers to the moment when the Centaur Upper Stage has completed a main engine burn and cuts off, entering a coasting phase.

Image source: Official site of NASA