The powerful NASA launch vehicle SLS carried the Artemis I mission one step closer to its goal of sending astronauts to the Moon and ultimately Mars. The payload of Orion is unmanned on this initial mission profile. It will go to the Moon and 26 days later be back to Earth.
The GOES-16 weather satellite currently in geostationary orbit frequently images the east coast in many wavelengths. It captured the launch seen here in this video clip.
What is MMOD? It is the acronym for Micro-Meteoroid and Orbital Debris. Space debris is a risk to other spacecraft both manned and unmanned. It includes derelict craft, fragments from their disintegration and collision, paint flecks, frozen liquids expelled from spacecraft, and unburned particles from solid rocket motors. The debris comes in a wide range of sizes from microscopic to bigger than a car. Most of it is small. There are estimated more than 128 million pieces of debris smaller than 1 cm (0.4 in), about 900,000 pieces of debris 1–10 cm, and around 34,000 of pieces larger than 10 cm (3.9 in) were estimated to be in orbit around the Earth.
The smallest size of debris like paint flecks and rocket exhaust particles are grouped with the small micrometeoroids from space in a group called MMOD. They pose a definite risk. Collisions with debris cause damage similar to sandblasting on spacecraft surfaces, to solar panels, and to optics like telescopes or star trackers. These small fast particles can puncture thin metals. Collision speed between 10 – 14 km/s (6 – 8.4 mi/s) are likely.
Several years ago I was evaluating science lessons for students who were preparing to take exams. One of these lessons from NASA posed some questions about the number of MMOD impacts felt by the Hubble Space Telescope. During the 2009 STS-125 Shuttle mission, the astronauts removed the Wide- field Planetary Camera 2 (WFPC2) and replaced it with the Wide Field Camera 3 (WFC3). Protecting the WFPC2 while it was aboard Hubble was a curved rectangular aluminum plate covered with white paint. A number of blemishes were observed from a distance on the painted surface and photographed with a telephoto lens from the Shuttle window. They are circled in this image. They were impacts from MMOD recorded during its 16 year exposure in space. More impacts were present but were too small to see from a distance.
Webb’s mirrors now direct fully focused light from space down into each instrument. This alignment allows each instrument is capture images. For the next two months, work will be done to commission each of the four scientific instruments. Performance appears better than the engineering team’s most optimistic predictions.
The NASA blog posted 28 April 2022 by Thaddeus Cesari describes the significance of this milestone in greater detail. Images in the post can be enlarged to show the great detail achieved by each instrument as well as the Fine Guidance Sensor. They are impressive. In addition, this one minute video from the blog summarizes the accomplishments.
Smarter Every Day author Destin interviewed his dad in 2016 who was working on the sunshield layers that were eventually placed on the James Webb Space Telescope. His dad worked as a metrologist who specialized in using sophisticated tools to accurately measure dimensions of products. In this video, several people explain the complex procedures used to measure the sunshield layers and how the data was fit to models and applied to the L2 point in space. It is a fascinating look behind the scenes at an essential part of the JWST. There is one ad break at the 15 minute time.
The JWST team successfully completed the third phase of mirror alignment by tilting each of the 18 segments to produce one image. This set of stacked images will further be refined by adjusting the heights of the segments to within one wavelength of light. This step is called Coarse Phasing. Details of the recently completed processes are here in their blog.
How I See It 