UPDATE: 4:05 p.m. EST - The countdown was put on hold at 3:23 p.m. EST and personnel checked on the "helium tank pressurization," according to a tweet from ULA. A new launch time of 5:11 p.m. EST was set after the issue was resolved, and the weather was at an 80 percent chance of favorable conditions, ULA tweeted

Original story:

United Launch Alliance is scheduled to make a third attempt at a rocket launch Friday afternoon. The Delta IV rocket is supposed to launch the NROL-47 mission for the National Reconnaissance Office, according to ULA.

If the launch is successful, it will be the 27th launch for the NRO and the 36th launch of the Delta IV rocket since it was first launched in 2002, according to ULA.

The launch was delayed twice earlier this week. On Wednesday it was scrubbed due to high winds at the Vandenberg Air Force Base where the launch is scheduled to happen. It was scrubbed again Thursday “Due to an issue with a ground system valve,” ULA said.

Coverage of the launch Friday is scheduled to begin at 3:40 p.m. EST, 20 minutes before the launch window opens at 4 p.m. EST. Less than three hours prior to the scheduled launch, ULA tweeted that there were no issues with the rocket or having to do with the launch at that time. The launch will be broadcast live on the ULA website as well as on YouTube.

Watch the ULA launch a rocket with an NRO payload here:

Little is known about the payload other than the fact that ULA is launching it for the NRO. Though NASA Spaceflight hypothesizes that it might be an imaging satellite

The NRO was formed in 1961 as a secret response to the launch of the Russian Sputnik. While it’s no longer a secret, it does still use its systems to collect information and “Play a crucial role in providing global communications, precision navigation, early warning of missile launches and potential military aggression, signals intelligence, and near real-time imagery to U.S. forces to support the war on terrorism and other continuing operations,” according to the NRO site.

The scheduled ULA launch comes less than a week after SpaceX launched a mysterious Zuma payload for the United States government and allegedly failed to deliver it to orbit.​​