The launch of NASA's Transiting Exoplanet Survey Satellite is postponed to Wednesday, April 18, due to needed additional GNC analysis.
SpaceX announces on Twitter that its teams are standing down today to conduct additional GNC analysis of TESS. Nevertheless, NASA assures that the spacecraft remains in excellent health and still ready for launch. It will still perform liftoff on a Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida as previously planned.
What Is GNC Analysis?
NASA says the system is a critical enabler of all launch vehicle and spacecraft system. Essentially, GNC keeps track of where celestial bodies are located in space and how far or near is the spacecraft within these bodies.
GNC maintains knowledge of the actual mission trajectory and ensures that the vehicle is within that route. To perform these functions, the GNC system uses different sensors and control devices.
GNC stands for three functions, namely Guidance, Navigation, and Control analysis.
"Guidance" refers to the actual steering of the spacecraft as it traverses the space. The command for guidance may come from a crew and computer on board or from radio commands.
"Navigation" refers to the size of the location where the spacecraft is moving in space. It also refers to the plotting of the course of the spacecraft.
Lastly, "Control" is the combination of "guidance" and "navigation" where the system or crew on board or at the station aligns and stabilizes the vehicle in space to remain in its planned course.
Take for example the Mars Reconnaissance Orbiter Mission. GNC is critical for the orbiter to correctly traverse to get to Mars, to precisely align its solar arrays pointing toward the Sun to keep power going, and to keep its antenna pointed toward the Earth to maintain communications.
In the case of the orbiter, GNC makes sure that the spacecraft is in its orbit and the cameras monitoring it are precisely within about 1/20th of one degree. The aim is to have the cameras captured substantial photos to be used for analysis on Earth.
The GNC maintains the cameras in angle amid the tiniest vibrations caused by solar arrays.
TESS To Look For As Much As 20,000 New Exoplanets
TESS is created in the hopes of capturing evidence of up to 20,000 new exoplanets and if they could harbor life. Specifically, it is designed for the stability needed for cameras to focus on the stars and the sky that the mission aims to explore.
TESS will look for stars 30 to 100 times brighter than those already observed by Kepler.
Standing down today to conduct additional GNC analysis, and teams are now working towards a targeted launch of @NASA_TESS on Wednesday, April 18. — SpaceX (@SpaceX) April 16, 2018