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Atacama Cosmology Telescope

Large dish points upward in rocky desert with mountains in the background.
Atacama Cosmology Telescope
Credit: ACT Collaboration

Telescope Details



Atacama Desert in Chile


Study how the universe began, what it is made of and how it evolved to its current state. More specifically, researchers aim to improve on measurements that describe the very early universe and measure large, distant clusters of galaxies and their environments.

NIST’s role:

NIST has contributed to three generations of ACT instruments, including superconducting sensors and electronics for two cameras, ACTPol, used 2013-2015, and the current AdvACT. For the latter, NIST invented the world's first multi-color camera for measuring the cosmic microwave background, helping to separate the true signal from interference such as galactic dust. The two-color camera effectively doubled the telescope’s capabilities, greatly reducing the time required to make very difficult observations.

Significant discoveries:

The first cosmological result from NIST’s two-color camera supported previously measured inconsistencies in values for the Hubble Constant, which describes the expansion rate of the universe. The results suggest that either there is a systematic error in one of the measurement methods or the current cosmological model is wrong.  

Other interesting facts:

Located at an altitude of 5,190 meters (17,030 feet), ACT is one of the highest permanent, ground-based telescopes in the world. The arid, high-altitude site avoids the problem posed by atmospheric water vapor, which emits microwave radiation that contaminates measurements. 

Supported by:

National Science Foundation 

Operated by:

Collaboration of 22 institutions led by Princeton University


Six-sided metallic plate has rows of pinkish sensors.
NIST sensor array in the AdvACT camera
Credit: NIST
Closeup of metallic plate shows circular sensors.
NIST sensor array in the AdvACT camera
Credit: NIST
Created September 30, 2021, Updated November 3, 2021