ISS Transits Sun | 6 Feb 2024

2024-02-062024-02-06Jim R 9 Comments

I received an email notice from a service a couple of weeks ago telling me of a solar transit by the International Space Station. The centerline was about 15 miles to my west. The transit was to last less than 2 seconds. The day of the transit was clear. I set up my camera and solar filter in a parking lot with a good view of the sky. I recorded video for a minute before and a minute after the expected transit at 9:17:50 am.

After returning home, I viewed the video and found the faint silhouette as it sped across the face of the Sun. With movie editing software, I cropped the video and slowed it down to 25% speed. The ISS appears at the 2 o’clock position, moves across to the left just above the center, and exits at the 8:30 position. It is most visible on a larger format screen. Don’t be surprised if you can’t see it. I followed the Watch on Youtube link and got the ‘best’ result.

If you like this sort of thing, I have a few other posts of transits of the Sun and the Moon by the ISS. Follow this link.

A Million People in the Air

2024-02-022024-02-02Jim R 24 Comments

While out for a walk during a recent sunny day, we noticed many passenger jets flying at high altitudes over us. They each have seating for dozens of people. An average of around 200 passengers per plane seems a reasonable estimate. We were curious about how many people might be up in the air at any one time around the world.

There are many flight tracking apps and websites that keep track of the aircraft. A web search of ‘flight tracker sites’ turned up a dozen or more. The one I use is ADS-B Exchange. If you open that link, click on View Map to see the world map of planes in the air. You can zoom into your location. This image below is a screen grab of the world map view.

Here is a screen grab of the zoomed-in view around Los Angeles and Las Vegas. A lot of planes were in the air when I got this image.

In your actual live map, click on any plane icon to see more details about that plane in the left margin. In the right margin, near the top, are two numbers for Total Aircraft and On Screen. Further down are some filters that can be applied to the results in the map. I chose to filter by Altitude. I set the lower limit to 20,000 ft and the upper to 40,000 ft. Most long distance carriers, such as the ones we saw during our walk, are within those altitude limits.

When I viewed the map this morning, the results filtered by altitude showed over 5000 planes flying that high. If there are about 200 passengers per plane, that means 5000 x 200 = 1,000,000 people are in the air this morning. I think that is a conservative estimate. There are several thousand other smaller low-altitude planes all over the world as well adding to that big number.

Sunglint Across South America

2023-09-12Jim R 4 Comments

The NOAA weather satellites GOES-East and GOES-West offer full disk views of Earth over the Atlantic and Pacific oceans. This image is from GOES-West in stationary orbit 22,300 miles above the equator over the central Pacific. At the time of this image, the Sun was directly behind the satellite illuminating the entire view. In the center is a brightened region of the ocean. It is caused by light reflected directly back to GOES off of the water and waves. Normally, water surfaces appear dark. This phenomenon is called sunglint. Several examples are shown at that link.

I looked at the full disk imagery from the GOES-East satellite to see if it was detecting clouds from tropical storms and hurricanes in the Atlantic. The images every 10 minutes are compiled and viewable as video. That imagery also showed sunglint during the daytime hours.

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Artemis I Launch Seen By GOES-16

2022-11-162025-09-11Jim R 11 Comments

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.

MMOD Impacts

2022-11-05Jim R 6 Comments

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.