A satellite imagery subscription service used by independent investigators and journalists to monitor events around the globe abruptly shut down Monday, and investigators with limited resources may have nowhere else to turn.

TerraServer, a vestigial limb of a Microsoft satellite imagery project from the 1990s, charged users a few hundred dollars a year for full access to its suite of high-definition satellite imagery, a much lower fee than other commercial services. Unlike Google Earth and similar free tools, TerraServer “was relatively up to date compared to other cheap and free services,” Eliot Higgins, founder of independent investigative collective Bellingcat, told Motherboard. This made it indispensable for investigations into human rights abuses in places difficult for journalists to access.

TerraServer was taken offline with no explanation on January 18 before the website was updated late Monday to announce the shutdown.

Investigators from around the world mourned the loss of TerraServer on Tuesday morning. Louisa Loveluck, the Baghdad bureau chief for the Washington Post, tweeted this was “a sad day” because TerraServer was “a vital tool” for their investigation into Syrian prison deaths.

“It’s pretty sad because they had an amazing amount of imagery,” said Fabian Hinz, a researcher at the James Martin Center for Nonproliferation Studies who used TerraServer for his work on missile studies in the Middle East. But Hinz added the interface was often cumbersome and difficult to use, which meant its potential was never realized.

According to Terraserver's FAQ page, the service is moving satellite imagery sales to TerraServer’s parent company PrecisionHawk, which bought TerraServer in 2015.

All accounts were deactivated as of Monday and given a pro-rated refund as of January 18. Users will “no longer have access to previously downloaded imagery” through the website, the FAQ page adds, before directing users once again to the PrecisionHawk order page (users who downloaded the images to their own drives will obviously still have access to their saved files).

While TerraServer offered a subscription plan that granted users virtually unlimited access to the company’s imagery, the FAQ states that PrecisionHawk will not offer a similar subscription plan. Instead, users will have to purchase images one by one or in batches, limiting their ability to proactively investigate sites in a cost-effective manner

PrecisionHawk did not immediately respond to a request for comment from Motherboard about why it shut down TerraServer or what the investigators who used it to research human rights abuses should do now.

Because Google Maps and Google Earth images are generally too old to be useful, investigators will have to resort to other, more expensive satellite imagery services.

Some services offer free or discounted subscriptions for NGOs, Higgins said, but that won’t cover all of the people who used TerraServer. “Those individuals who make up a lot of the online open source investigation community whose only option for up-to-date satellite imagery is TerraServer will be impacted the most from this.”