The red signals have been one of Star Trek: Discovery season 2's primary mysteries, but the penultimate episode, "Such Sweet Sorrow," has now clarified the true purpose of the bursts of light in space. With five of the seven red signals now revealed, we know how they factor into the final battle against the evil A.I. called Control that wants to end all sentient life in the galaxy, and who sent the red signals in the first place: a future version of Michael Burnham.

Most of Star Trek: Discovery season 2 was focused on learning the identity of the time-traveling Red Angel, who was revealed to be Michael's mother, Dr. Gabrielle Burnham. However, Gabrielle claimed that in her 841 failed attempts to stop the timeline where Control annihilates the galaxy, she never sent any red signals to warn the Discovery. Compounded with the Red Angel's DNA match to Michael, Spock concluded that Michael herself was a second Red Angel who sent the red signals from the future. This also means that future Michael is partially responsible for Spock's mental breakdown earlier in the season, though it was the present version of Burnham who enabled the healing of Spock's mind with the help the psychic inhabitants of Talos IV.

Related: Star Trek: Discovery's Burnham Story Homages DS9's "The Visitor"

The first three red signals led the U.S.S. Discovery on rescue missions, but it later became clear the starbursts were being sent by an individual with conscious design: Michael herself. Once Michael realized she was also the Red Angel in "Such Sweet Sorrow," Burnham decided on her plan to save the galaxy: she would wear a newly-built Red Angel time suit to tow the U.S.S. Discovery into the far future to keep the sphere data that Control needs to evolve and achieve consciousness away from the A.I. Unfortunately, it would be a one-way trip and Michael would be unable to return to the 23rd century. But once she is in the future, Michael would then send the red signals to enable the Discovery to achieve the vital steps necessary to enable her plan in the first place.

As Star Trek: Discovery season 2 plays out its endgame, here is the purpose of the five red signals that have been revealed thus far and what important steps they led the Starfleet Officers to take in order to save the galaxy:

Red Signal #1: Rescue Jett Reno

The red signals first appeared in Star Trek: Discovery's season 2 premiere, "Brother." The first signal led the Discovery to an asteroid field and the crashed U.S.S. Hiawatha, which had been there for 10 months and eleven days after being damaged during the Klingon War. There, Michael Burnham, Captain Pike, and Commander Nhan met Commander Jett Reno, a Starfleet engineer who had rebuilt the ship's medical equipment to keep some of the Hiawatha's crew alive. The Discovery crew rescued Reno, though Michael was injured in the escape and saw a vision of the Red Angel.

Rescuing Jett was the purpose of the first red signal. Reno isn't just an acerbic comic foil for Lieutenant Paul Stamets; as a brilliant engineer she is vital in making sure the time crystal is able to be sufficiently charged so that Michael's Red Angel suit can open a wormhole into the future. Jett also received a vision from the crystal about specific damage the Starship Enterprise will incur in the battle against Section 31's fleet; she could then be vital in saving Captain Pike and his crew in the season 2 finale. Basically, without Jett Reno coming aboard the Discovery, Ensign Sylvia Tilly would be lost in the mycelial network and Burnham's time travel gambit would automatically fail.

Related: Star Trek: Discovery's Homage to Wrath of Khan (And What It Reveals About Spock)

Red Signal #2: Find Terralysium

The second red signal led the Discovery to a planet in the Beta Quadrant called Terralysium, as seen in the second episode, "New Eden." At Terralysium, Pike, Burnham, and Lieutenant Owosekun found over 11,000 human beings descended from a group that was originally from Earth. Their ancestors were saved from a World War III nuclear holocaust by the Red Angel and transported to the Beta Quadrant. The multi-faith-worshipping people on Terralysium abandoned technology and were subsequently saved from an extinction-level event by the Red Angel and the U.S.S. Discovery.

It was vital that the Discovery's crew learned about Terralysium, which was the purpose of the second red signal. The Red Angel/Dr. Gabrielle Burnham was using Terralysium as her home base and anchor point for time traveling from 950 years in the future. Because Terralysium lacks technology, it's a haven from Control, which had conquered the galaxy. Part of Michael's plan involves hiding the Discovery at Terralysium in the future to keep the sphere data safe from Control.

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Red Signal #3: Liberate Saru's Homeworld

The third red signal brought the Starship Discovery to Kaminar in the sixth episode, "The Sounds of Thunder". For hundreds of years, First Officer Saru's homeworld had been subjugated by the technologically superior Ba'ul. In "An Obol for Charon," the Red Angel had placed the dying sphere in the Discovery's path so that the ship would integrate its 100,000 years of data - Dr. Burnham hoped this would safeguard the data from Control. But proximity to the sphere also triggered Saru's Vahar'ai, the Kelpien process of evolution. Now changed, Saru fought to evolve the Kelpiens to liberate Kaminar from the Ba'ul.

It's not clear exactly what role Saru or the Kelpiens have to play in Michael's endgame plan to defeat Control. As Acting Captain of the Discovery, perhaps the fact that Saru is now free of fear will be vital in the battle against Section 31. It's also possible that the future Michael wanted to ensure that Saru and the Kelpiens achieve their desperately-needed evolution, simply because she loves Saru like family. It's also a longshot but, in the time since the Kelpiens beat the Ba'ul thanks to the Red Angel, Saru's people may have learned enough about the Ba'ul's technology that they can use it to join in the fight against Section 31.

Related: Did You Catch Star Trek: Discovery's Futurama Reference?

Red Signal #4: Get A Time Crystal

The 4th red signal brought the Discovery to the Klingon planet Boreth in season 2's 12th episode, "Through the Valley of Shadows." The ancient monastery on Boreth has a secret purpose: to protect the time crystals that are native to the planet. Captain Pike traveled alone to the monastery to retrieve a raw time crystal, which is vital to the Discovery's plan to hide the sphere data in the far future to keep it away from Control.

While he was at Boreth, Pike was guided by the albino Klingon Tenavik, who is the son of High Chancellor L'Rell and Voq/Ash Tyler. Tenavik, who was brought to Boreth as an infant a few months prior and is now fully grown thanks to exposure to the time crystals, warned Pike about the price he must pay to take one away from the planet. Pike saw his tragic future (which Dr. Burnham alluded to) - that he will be horribly disfigured by delta rays and, by taking the time crystal anyway, the heroic captain chose to lock himself into that destiny. Still, Pike understood the purpose of the 4th red signal was to secure a raw time crystal and he willingly sacrificed his own future to save the galaxy.

Red Signal #5: Get Po To Charge The Time Crystal

The fifth red signal brought the Discovery to Xahea, which is ruled by Tilly's friend, Me Hani Ika Hali Ka Po. The teenage queen first appeared in the Short Trek episode "Runaway" when she stowed away aboard the Discovery and befriended Tilly. Their warm relationship was instrumental in securing Po's help in powering the time crystal so that the second Red Angel suit built to be worn by Michael Burnham would be able to time travel.

It was clear why the fifth signal led our heroes to Xahea and her queen: Po is a genius inventor who designed an incubator to re-crystalize dilithium - her technical know-how was necessary to build a power source that could charge the Discovery's raw time crystal. Essentially, Po built an incubator that could replicate the energy of a supernova in order to charge the time crystal. Po also built "siege weapons" to help the Discovery and the Enterprise fight Control's fleet - and she may even have volunteered to join her Starfleet friends as they jump to the far future.

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There are still two more red signals to be revealed, which will hopefully occur in Star Trek: Discovery's season 2 finale. What role they have to play in Michael Burnham's endgame to save the galaxy - and whether her plan will work - remains to be seen.

Next: Star Trek Theory: Discovery Season 2 Is The Borg's Origin

Star Trek: Discovery's season 2 finale streams Thursday, April 18 on CBS All-Access and internationally the next day on Netflix.