Satellite imagery indicates that North Korea has completed upgrades to a rocket launchpad in the country’s northwest and is proceeding with work to install a cover over it, diplomatic sources familiar with the developments said Saturday.

U.S. intelligence agencies, believe the cover at the launch site in Tongchang-ri, North Pyongan province, is an attempt to evade surveillance by spy satellites, the sources said.

There are no indications that a rocket has been placed on the pad at the site, called the Sohae Satellite Launching Station.

North Korean leader Kim Jong Un reportedly instructed the country’s National Aerospace Development Administration earlier this year to launch a satellite to mark the 70th anniversary of the founding of the ruling Workers’ Party of Korea on Oct. 10, fueling speculation of a series of provocations in October.

The United States, Japan and South Korea suspect the project will effectively be a test-launch of an intercontinental ballistic missile the country is allegedly developing.

According to analysis by U.S. intelligence agencies, the cover installation work is to be completed sometime this month. Details of the cover, such as its shape and whether it will be removed for the launch, are unclear.

In 2012, North Korea conducted two long-range rocket launches from the Tongchang-ri complex that were condemned by the international community. For both launches, the parts were transported from a factory near Pyongyang via train to the launch site, where they were assembled into a three-stage rocket. At the final stage of each of the launch preparations, a cover was placed on the side and other locations of the launchpad.

The U.S. estimated the timing of each launch, and together with Japan and South Korea tracked the missiles with Aegis-equipped cruisers.

For the upcoming launch, a roof has been constructed that completely encloses the platform of the rail line that extends into the launch site. As a result, following the preparations and the shape of the missile will likely be more difficult than before.

According to the diplomatic sources, the previous 50-meter-tall gantry at the site has been extended to 60 meters in height. Military and intelligence officials believe the facility is now capable of firing long-range missiles twice the size of the 30-meter-long Unha-3, which Pyongyang claims was used to put a satellite into orbit in December 2012.