As many of you know the OSIRIS-REx spacecraft made an Earth gravitational assist fly-by today. The spacecraft needed the slingshot maneuver to make it to its rendezvous with the asteroid Bennu in August 2018. The spacecraft will orbit the asteroid for up close study, then drop low enough to grab a sample of the surface for return to the Earth in September 2023.
NASA put out a call to amateur astronomers to take images of the spacecraft as it approached the Earth. So, for the past week I have been attempting to do just that. Last night the spacecraft was finally bright enough for me to catch it in a series of exposures. Even so, the speed, brightness and size of the spacecraft makes it very difficult to see.
The above image is the third of eight 300 second exposures that I was able to get before the clouds closed in. The circle shows the location of the automobile sized craft which should give you an idea where it will be in the following animation. The craft’s motion is from upper right to middle left.
I had to stretch the images as well as invert them to make the faint streak a little more visible. This close to the Earth the apparent velocity of OSIRIS-REx is obvious.
This morning the Cassini spacecraft entered the atmosphere of Saturn and ultimately became part of the planet it was sent to study.
Artist rendering of Cassini’s atmospheric entry. Credit: NASA/JPL
The spacecraft entered orbit around Saturn on the 1st of July 2004 after a six year trip to the planet. It has been studying Saturn and its rings and moons since that time. One of the first things the spacecraft did was to deploy the Huygens probe toward Saturn’s largest moon, Titan. The probe became the first lander on a solar system moon other than our own.
Artist rendering of Huygens’ landing on Titan. Credit: NASA/JPL
Image from the surface of Titan. Credit: ESA/NASA/JPL/ University of Arizona
There are too many discoveries over the 13 years Cassini spent in the Saturnian system to list. Probably the most surprising was the discovery of geysers erupting from the southern pole of the ice covered moon Enceladus.
Geyser plumes from the southern pole of Enceladus. Credit: NASA/JPL
Subsequent study has revealed the material being ejected from the moon to be salty water carrying organic molecules. This implies the conditions necessary for life exists in the outer solar system in a place scientists never expected.
In addition to the scientific discoveries is the vast archive of images that Cassini took. The beauty of the planet and rings was worth the investment.
Saturn as seen by Cassini. Credit: NASA/JPL
To the entire Cassini/Huygens team, thank you. Well done.
Last night I took images of a comet. My standard exposure length of 300 seconds was too long and during that period the comet moved enough to smear into a streak rendering the images useless for analysis. The video is an animation of 11 300 second exposures and shows the amount of movement over 55 minutes. In this case, North is to the top.
Currently, the comet is between Mars and Jupiter and above the plane of the ecliptic but headed south to where most of its orbit lies.
I will try a different tracking technique and exposure duration later tonight to see if I can get accurate astrometric data to report to the MPC and to get a prettier picture of the tail.
The PTO has one camera dedicated to meteor search. The All-Sky camera that feeds the PTO web site Sky Conditions page and the Weather Underground can also detect meteors if they are bright enough. The problems with both of those are the tree line at the PTO and the bright local sky. I wanted a meteor camera that I can take to dark sky locations. So, I cobbled together a spare camera and a lens. I was finally able to test the system on the 12th of August. Several members of the NWFAA met at a dark site near Munson, FL to observe the Perseid meteor shower peak on Saturday evening.
The system consists of a video camera that feeds a GPS time inserter so each video frame can be time stamped. The output video stream is fed to an analog-to-USB converter dongle which then feeds a laptop running meteor detection software. In my case, the software is HandyAvi. The camera is a WATEC WAT-902H2 Ultimate and has a Fujinon 1.4mm fisheye lens on it.
I arrived at the observing site well before sunset so I could set everything up in daylight. The picture supplied by the system was very sharp and bright. But the darker the skies got, the more the picture deteriorated and by the time the sky was fully dark, the picture was so noisy as to be unusable. I tried rerouting power and signal cables and restarted the camera to no avail. So, I shut everything down, packed up and reverted to visual observation. Unfortunately, the cloud cover prevented viewing all but a couple of meteors and eventually we all gave up.
Once home I re-assembled the system in the back yard for some additional testing. I was able to reduce the noise by switching to a manual gain control mode, but even then the camera did not show anything but Vega and a local street light. The camera does not have an integrating mode so it is not as sensitive as I would like.
I regrouped and switched to a different camera. This one is a Imaging Source DMK-21AU618 USB camera and is capable of integrating its output. I don’t currently have a way to insert a time stamp. However, even if the software can detect a meteor, there is no way to know when in the integration time period the meteor struck, so a very accurate time code is not useful.
So, back into the back yard. During the test, the PTO was running an asteroid observing plan. Notice the dome tracking the night sky. There are flashes from local traffic and what appears to be one short satellite trail. Just by looking at the star patterns, the limiting magnitude is right about 6.0. Not only are the star clouds of the Milky Way visible, about 5 seconds into the video, the Andromeda Galaxy comes into view. It is only a small fuzzy smudge, but it is visible. Just before the video ends some glare from the rising Moon starts to intrude. The video is a animation assembled from 282 twenty second exposures.