NASA has once again postponed the launch of a small rocket from the coast of Virginia tonight, blaming cloudy skies at observation locations. The craft — a Terrier-Improved Malemute sounding rocket — was set to create multicolored clouds high in the sky for the purposes of studying our planet’s ionosphere and aurora, but the mission has been repeatedly scrubbed a short time before launch due to bad weather.

When the launch does eventually go ahead, the rocket will release canisters filled with various chemicals, forming green and red artificial clouds that may be seen along the US East Coast. It’s all part of a plan to study how particles move in the upper atmosphere, which could help us better study the aurorae and the parts of our atmosphere that are electrically charged by solar and cosmic radiation.

Don’t worry, the chemicals the rocket is releasing are in no way toxic to your health. They’re vapor tracers — gases that create visible clouds high in the sky. They’re made of barium, lithium, and tri-methyl aluminum. Those chemicals may not immediately sound familiar but you have likely seen them in action before — in fireworks. And fireworks usually release a whole lot more of these gases than a typical NASA mission, according to the space agency.

NASA has been deploying vapor tracers for a while now using sounding rockets, the small vehicles designed to take instruments to sub-orbital space. Though NASA is testing out a new method for getting those vapor tracers into the upper atmosphere. Normally, the tracers were released directly from the rocket’s main payload, but this mission’s rocket is carrying up a specialized contraption called the “multi-canister ampoule ejection system.” After launch, the instrument will fling out multiple canisters filled with the tracers, in order to cover a wider area of the sky.

A total of 10 canisters, each about the size of a soda can, will be deployed about 4 to 5.5 minutes after launch, NASA says. The multicolored clouds they create will give researchers visual cues to help them track the movements of particles at high altitudes and test out if our models of these particle motions are correct. And these clouds should be pretty high up, too, since the canisters will release the tracers between 96 and 124 miles up. If skies are clear, the clouds could be seen from New York to North Carolina.

NASA has been trying to get this sounding rocket up for a while now. The launch was originally scheduled for May 31st, but it has been repeatedly postponed due to bad weather. The space agency also tried on the evening of June 11th and 12th, but launches were canceled, first due to wayward boat within the launch range, and then because visibility was too poor for the rocket’s tracers to be seen from observation stations. Tonight’s launch was slated to get off the ground sometime between 9:04PM and 9:19PM ET, but was scrubbed when the clouds didn’t clear up in time.