Good evening, skywatchers.
On January 21, 2018, New Zealand private company Rocket Lab launched a rocket carrying four satellites from its base in New Zealand. Three of the satellites are small earth observation satellites. The fourth serves no commercial purpose but is very unique. It is a carbon fiber sphere one meter (39 inches) in diameter and weighs almost 23 pounds. The sphere is covered with 76 triangular-shaped facets made of highly reflective polished material. Rocket Lab's CEO and founder Peter Beck arranged for this object to be launched into orbit around the earth as a public awareness mission to create a shared experience for everyone on planet earth. The satellite essentially functions as a giant disco ball that reflects sparkles of light back to earth. It orbits the earth once every 92 minutes from an average height of 235 miles above ground. However, the satellite is only visible under exactly the right conditions. If it passes above us during the daytime, the sun's glare will completely drown out any sparkles. If it passes above late at night, the satellite will also be in the dark and reflect nothing toward us. It has to be passing high above us shortly after sunset or shortly before sunrise. That combination of circumstances will be optimal only at certain times of the year. And we have to look at the right time in the right direction to see it.
Generally, the Humanity Star takes about eight minutes to travel across our local sky. It either comes out of the north and sets in the far south or vice versa. Mid-March and mid-May of this year are predicted to be the best months to spot it. I went out and observed it on Sunday, March 11 at 7:15 p.m as well as on the following Sunday, March 18th, at 5:50 a.m. It's tricky and is really only easy to see when high overhead. I saw instantaneous flashes of light that resembled the strobe light on a small, distant Cessna airplane. Each flash occurred during the instant in which one of the tumbling satellite's facets reflected the sun straight towards me. The flashes occurred about once every two seconds and were about as bright as an airplane's strobe light far in the distance. I saw nothing but darkness between flashes. The flashes were not always the same brightness. Sometimes I would see two bright flashes followed by a dim, barely visible flash, followed by a brighter one. The flashes were travelling across the sky about as quickly as a fast airplane. To get an idea of what to look for, you can watch the YouTube video
. This was a particularly good sighting recorded in New Zealand.
You can read about this public awareness mission at thehumanitystar.com
I ran the satellite's TLE data from NORAD through three computer programs and generated the following predictions for the next week. There will be a couple of favorable appearances in the early morning hours in the Tucson area. Of course, the weather is another crucial factor when looking for the satellite. Not only must a viewer be looking in the right place at the right time, the sky has to be clear as well! At 200 miles above the earth, the satellite is travelling far above the highest clouds. Hence, a cloudy or overcast sky will block the view and Tucson's weather can be iffy in March.
Mon. Mar. 19. Comes out of the north at 5:48 a.m. Halfway overhead to the west, at 5:51:30 a.m. (It will be moving fast and the seconds do count.) Passes near the bright red star Arcturus (pointed to by the handle of the Big Dipper and often mistaken for Mars) at 5:51:32 a.m. Passes near Jupiter, the brightest point of light in the sky at this time, at 5:52:12. Disappears into the south at 5:55 a.m. The sky will be fairly light at this time, making the satellite difficult to spot. Use a very accurate clock and the star and planet as reference points. 218 miles away at its closest approach.
Tue. Mar 20. The poorest appearance of those described here. Comes out of the north at 5:45 a.m. Less than halfway overhead to the west at 5:48:40. Passes below the star Arcturus at 5:48:44. May be challenging to see when it passes below Jupiter at 5:49:32. Disappears into the south at 5:52 a.m. 265 miles distant at its closest approach.
Wed. Mar 21. Another fair to poor appearance but worthy of those who like a challenge in a darker sky. Comes out of the north at 5:37 a.m. A little more than a third of the way overhead to the west at 5:40:40 a.m. Passes quite a bit below Arcturus at 5:40:46 and quite a bit below Jupiter at 5:41:32. Disappears into the south at 5:44 a.m. The satellite will be a distant 261 miles from us at its closest approach. As an added bonus, the International Space Station will cross the sky in a similar direction about 14 minutes earlier. It will emerge in the west out of the earth's shadow at 5:27 a.m., come near Jupiter at 5:27:56, and set near the southeastern horizon at 5:32 a.m. The ISS will be very bright (magnitude -1.9), as bright as Jupiter!
After this, the orbit will devolve into less favorable viewing appearances for watchers in Tucson. It's also important to be aware that the satellite's orbit cannot be predicted with any precision at all beyond five to seven days in advance. Let me know if you wake up early and see it this week!
Contrary to Rocket Lab's and Peter Beck's expectations, the Humanity Star's orbit has just begun decaying rapidly and precariously. Two satellite-tracking websites are predicting that the Humanity Star will re-enter earth's atmosphere this Thursday, March 22nd. One of those sites predicts that the satellite will come down in the south Pacific. The satellite, which was launched on January 21st and intended to have a 9 month lifespan, will thus have survived only 2 of those 9 months. The problem apparently lies in the satellite's surface area to weight ratio. It's a meter in diameter but only 1 mm thick. For that reason, it doesn't weigh much for its size. This means that the 23 pound satellite doesn't have much momentum as its proportionally large surface area pushes through the rarefied air of the upper atmosphere. While the Humanity Star experiences the same amount of drag force as a similarly sized conventional satellite, the lack of weight and lower momentum means the drag will slow it down more, causing it to fall from orbit sooner. It's a good thing some of us observed it when we did, as the opportunity to see one of the pioneering private space projects is about to come to an end.
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