The Mainframe, also called the main structural component, is the backbone of the instrument. All of the instrument’s internal components are attached to the mainframe in some way, supporting a total of 185 kg of weight while maintaining its structural integrity at all orientations. While it is in space, the instrument will not always face the Earth, therefore structural integrity is especially important. MODIS and Aqua/Terra are periodically required to change their orientation to view the Sun, the Moon, or deep space, or to perform various maneuvers that will change the location of gravitational pressure on the Mainframe.

Technical Description

The Mainframe is composed of a combination of sheets and hot-pressed blocks of beryllium. There are a total of 50 parts making up the whole of the Mainframe, all of which are bolted and bonded together to provide precise mounting surfaces for the various internal components, such as:

•The telescope

• Aft optics

• The Scan Mirror

• The Passive Radiative Cooler

• Four calibration assemblies

•Three anti-contamination doors

• Three kinematic mounts which anchor the Mainframe to the satellite


The three primary load-carrying bulkheads are the Optical Bench Bulkhead, the Calibration Bulkhead, and the Zenith Bulkhead.

• The Optical Bench Bulkhead has machined features for bolting the Main Electronics Module in a cold space view direction and pseudo-kinematic mounts for the alignment of the Optical Bench.

•The Calibration Bulkhead precisely aligns and supports the Scan Mirror Assembly, Blackbody, Spectroradiometric Calibrator Assembly, and Solar Diffuser Stability Monitor.

•The Zenith Bulkhead ties these primary bulkheads together and provides a three-point mount for the Solar Diffuser.


The Mainframe fits within a dimensional cube that measures 1.2 m X 1.0 m X 1.0 m and weighs 43 kg.