Honestly, this week was kinda boring, so instead of discussing nothing interesting, we’re going to cheat and look back at yet another event that was packed into last week, specifically, April 18, 2018.

At 22:51 UTC, the Transiting Exoplanet Survey Satellite, also known as TESS, launched atop the last new SpaceX Falcon 9 Block 4 rocket from SLC-40 at Cape Canaveral in Florida. A quick aside about Block 4 versus Block 5 boosters: the Block 4 boosters were plain white and lacked the improved thermal protection and other components that improve reuse of the first stage compared to the Block 5 boosters that flew every mission after TESS. Block 4 boosters were only capable of two flights while Block 5 boosters have demonstrated nine flights, with more planned in the future.

Anyway, back to TESS. The first stage of the rocket that launched TESS cut off and separated after two minutes and thirty seconds of flight and landed safely on the drone ship Of Course I Still Love You. The second stage continued to take the spacecraft to a highly elliptical initial orbit of 200-km by 270,000-km! This highly elliptical orbit allowed TESS to get close enough to the Moon’s orbit to get a gravitational assist from Earth’s natural satellite, putting it in a 2:1 Moon-resonant orbit around the Earth, meaning that it would orbit the Earth once for every two Moon orbits.

The high eccentricity of the orbit also meant that TESS would spend most of its time away from the Earth with a clear view in almost all directions. That clear view is really important because TESS needs to be able to observe as many nearby stars as possible. TESS is stargazing with a mission: try to find exoplanets around far-away stars by using the transit method. When a planet passes between a star and an observer, also known as a transit, the star will dip in brightness for a short period of time. TESS is able to keep track of where and when these brief periods of dimness occur by taking lots of pictures of the sky over time, which astronomers and other researchers are then able to compare those pictures to figure out which stars dimmed with a consistent pattern.

TESS’s first observation happened not to be an exoplanet but rather comet C/2018 N1, which was previously discovered by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer project, or the NEOWISE Mission, and should not be confused with Comet C/2020 F3 from last summer that was also known as Comet NEOWISE (confirming once again that astronomers should not be allowed to name things). C/2018 N1 was spotted on July 25th, 2018, during a test of TESS’s instruments to make sure that the craft could take stable periodic pictures of a broad region of the sky for a long period of time. The test also showed that TESS was apparently extremely good at detecting and identifying variable stars, whose brightness changes and pulsates, which was a good indication of its ability to detect changes in eclipsed stars as well, aiding in its hunt of extrasolar planets.

The first exoplanet TESS discovered was on September 18, 2018, a super-earth in theπ Mensae system, a system previously discovered to have a super Jupiter orbiting around its star. The newly discovered planet seems to be twice the size of the Earth, around five times the Earth’s mass and orbits its host star once every 6.27 Earth days.

TESS is still operational, having had its mission extended past its original planned span of two years, and as of writing this, it has discovered 2647 exoplanet candidates with 122 confirmed. We look forward to seeing what the future holds for TESS, and we’ll bring you key results as we learn them right here at Daily Space.

More Information

Launch video

Launch Profile – Falcon 9 – TESS (Spaceflight 101)

TESS Orbit Design (Spaceflight 101)

NASA’s Planet-Hunting TESS Catches a Comet Before Starting Science (NASA)

“TESS Discovery of a Transiting Super-Earth in the pi Mensae System,” Chelsea X. Huang et al., 2018 November 30, The Astrophysical Journal Letters