Archive
10/04/2021 – Ephemeris – Why we can’t talk to the Perseverance rover on Mars right now
This is Ephemeris for Monday, October 4th. Today the Sun will be up for 11 hours and 32 minutes, setting at 7:17, and it will rise tomorrow at 7:46. The Moon, 2 days before new, will rise at 6:30 tomorrow morning.
NASA is no longer sending commands to its Perseverance rover or any of its assets roving or orbiting Mars now. The reason isn’t particularly sinister. It’s the approximately 26 month Mars solar conjunction. The Sun is a noisy radio source, and commands sent to or data received from these martian assets could be garbled. This affects everyone’s assets on or orbiting Mars, which includes the Europeans, India, China and the United Arab Emirates. For NASA, communication restrictions started two days ago and will last until the 14th. This will give the folks at JPL who are operating the Curiosity and Perseverance rovers some time off, and time to plan the next few months of activity.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4 hours). They may be different for your location.
Addendum
Mars in solar conjunction. Looking at the inner solar system. Mars, near the bottom of the image, is 244.6 million miles (393.9 million kilometers) from Earth. Click on the image to enlarge it. Credit NASA’s Eyes app.
Mars beyond and to the upper left of the Sun yesterday. It’s tough to get intelligible radio signals through the solar corona. Credit: NASA/ESA SOHO* spacecraft. The annotation is mine.
* SOlar and Heliospheric Observatory, spacecraft in halo orbit around the Lagrangian L1 equilibrium point about 930,000 miles (1,500,000 kilometers) sunward of the Earth. This keeps the satellite roughly between the Sun and the Earth, instead of moving ahead of the Earth because it’s closer to the Sun.
06/22/2021 – Ephemeris – Mars is poised to cross in front of the Beehive Star Cluster tonight
This is Bob Moler with Ephemeris for Tuesday, June 22nd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:57. The Moon, 2 days before full, will set at 4:41 tomorrow morning.
Tonight, the planet Mars will be at the western edge of the Beehive star cluster. Tomorrow night, Mars will be seen against its stars. Normally, the Beehive star cluster is easily seen in binoculars. The problem is, that both the cluster and Mars will be low in the west-northwestern sky, only six to seven degrees above a sea or lake horizon near the optimal time to spot them of 11 pm. It has been 8 months since Mars was opposite the Sun in our skies, and relatively close to us. Back then it was as bright as Jupiter and relatively close to the Earth. Now, Mars is 221 million miles (356 million kilometers) and 5 times farther aw0ay, about half the distance to Jupiter. It’s tiny in telescopes and very hard to pick out of the dim twilight glow of 11 pm.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4). They may be different for your location.
Addendum
Mars passing in front of M44 as a GIF animation. This is difficult to spot with binoculars low in the west-northwest at 11 pm on the nights of June 22nd, 23rd and 24th. The Beehive star cluster is a relatively close and sparse cluster. On dark nights in early spring, the cluster looks like a fuzzy spot to the naked-eye. It reveals its true nature in binoculars. Created using Cartes du Ciel.
02/23/2021 – Ephemeris – The Perseverance rover landed on Mars taking video all the way down
Note: There was a news conference at JPL, Monday at 2 pm EST where videos of the parts of the landing were shown. Most hadn’t made it to the https://mars.nasa.gov website by Monday night. The news conference with the videos can be found on NASA TV, NASA’s YouTube channel and other sites.
This is Ephemeris for Tuesday, February 23rd. Today the Sun will be up for 10 hours and 52 minutes, setting at 6:22, and it will rise tomorrow at 7:28. The Moon, halfway from first quarter to full, will set at 6:15 tomorrow morning.
It looks like the Perseverance Rover was gently lowered to a flat spot in Jezero crater on Mars about a kilometer or two from the edge of the river delta it was aiming to be near. It is in the midst of checkouts and the unfolding of its masts and its various appendages. For the third time the Mars Reconnaissance Orbiter was able to take a picture of the entry craft on its parachute seen above the delta, as it had with Curiosity and the Phoenix lander before all the while performing its communication relay duties. A few images have come back from Percy, as the Rover is nicknamed as I record this Sunday night. By Monday Percy should have sent back more images and perhaps parts of the landing video.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
A frame from the video looking down at the Perseverance rover from the Sky Crane. In the video as the rover neared the ground it was enveloped by a cloud of dust, so the support lines simply disappeared into the cloud of dust that enveloped the rover. Click on the image to enlarge. Credit NASA/JPL.
The Perseverance rover on the parachute over Jezero crater from the Mars Reconnaissance Orbiter. The circle on the image is the point where the rover landed. Click on the image to enlarge. Credit NASA/JPL-Caltech/University of Arizona.
02/18/2021 – Ephemeris – The Perseverance Rover will land on Mars this afternoon
This is Ephemeris for Thursday, February 18th. Today the Sun will be up for 10 hours and 37 minutes, setting at 6:15, and it will rise tomorrow at 7:36. The Moon, 1 day before first quarter, will set at 1:30 tomorrow morning.
Later this afternoon the Perseverance Rover will land in Jezero crater on Mars. NASA will have a live Internet feed from the Jet Propulsion Laboratory starting at 2:15 pm EST (19:15 UTC). Atmospheric entry will be at 3:48 pm EST (20:48 UTC), landing at 3:55 pm EST (20:55 UTC). This is Earth received time. The events actually happened 11 minutes 22 seconds earlier on Mars. Though cameras on the spacecraft will be recording the landing activity it will not be sent to Earth in real time due to the weak signal during entry. The spacecraft will be sending tones only for specific events during what is called EDL, Entry, Descent and Landing or “Seven Minutes of Terror”. If all goes well the first images will be taken and sent of its surroundings. And in the next weeks we’ll get an actual replay sent back of the landing with color and sound. It will be so cool!
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Links
NASA on YouTube: https://www.youtube.com/results?search_query=nasa
NASA TV: https://www.nasa.gov/multimedia/nasatv/#public
Graphic of the Entry, Descent and Landing of the Perseverance Rover. Click on the image to enlarge. Credit: NASA/JPL.
Perseverance drilling for a sample in Jezero crater. Artist drawing – NASA/JPL
02/16/2021 – Ephemeris – Perseverance lands on Mars in two days
This is Ephemeris for Fat Tuesday, Tuesday, February 16th. Today the Sun will be up for 10 hours and 32 minutes, setting at 6:13, and it will rise tomorrow at 7:39. The Moon, 3 days before first quarter, will set at 11:24 this evening.
In two days, Thursday afternoon, the Perseverance Rover will land on the planet Mars in a crater call Jezero. It’s mission to actually look for evidence of past life, fill specimen tubes to be cached for later pickup and returned to earth by a future mission, presumably by the end of the decade. It is also bringing a helicopter drone named Ingenuity to check out the feasibility of using future aircraft in Mars rarefied atmosphere. The vehicle, including the back shell and descent stage sports 23 cameras. Even Ingenuity has 2 cameras. That shouldn’t be a big deal today. Heck, my smartphone has 5 cameras, each with lots more megapixels than the digital camera I bought 15 years ago. Only two days to go to landing.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Graphic of the Entry, Descent and Landing (EDL) of the Perseverance Rover. Click on the image to enlarge. Credit: NASA/JPL.
02/09/2021 – Ephemeris – Happy Mars New Year
This is Ephemeris for Tuesday, February 9th. Today the Sun will be up for 10 hours and 11 minutes, setting at 6:03, and it will rise tomorrow at 7:49. The Moon, 2 days before new, will rise at 7:35 tomorrow morning.
Thanks to Dr. Phil Plait’s Bad Astronomy Blog I found out that last Sunday was Mars’ New Year’s Day for year 36*. I didn’t know they were counting them. Year 1 started on the first day of spring for Mars’ Northern Hemisphere, April 11th 1955. Like for most calendars the year numbering wasn’t created until later, from a scientific paper published in 2000 which followed the seasonal changes on Mars and had to put them in Mars years to make sense, rather than Earth years. I approve. As a teenager with my first telescope I eagerly awaited Mars’ especially close approach in 1956. By the Mars calendar that was in martian year 1. Back then our ignorance of Mars was profound. But a decade later the Mariner 4 spacecraft flew past Mars taking the first closeup pictures.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
* For some reason I said it was year 38 in the broadcast.
Addendum
Earth and Mars orbits and seasons compared as seen from the north. Planet motion is counterclockwise. Vernal equinox is the position of the planet for the Northern Hemisphere spring Source: Wikipedia user Areong.
Additional links:
https://www.syfy.com/syfywire/happy-martian-new-year
https://en.wikipedia.org/wiki/Timekeeping_on_Mars
https://www.planetary.org/articles/mars-calendar
01/21/2021 -Ephemeris – The Perseverance rover is less than a month from landing on Mars
This is Ephemeris for Thursday, January 21st. Today the Sun will be up for 9 hours and 24 minutes, setting at 5:36, and it will rise tomorrow at 8:11. The Moon, 1 day past first quarter, will set at 2:40 tomorrow morning.
The Mars Perseverance Rover is approaching the Red Planet. In a bit less than a month, on February 18th it will plunge into the martian atmosphere to land near an ancient river delta in the 28 mile (45 kilometer) wide crater Jezero. The dramatic entry-descent-and-landing or EDL is what the Jet Propulsion Laboratory, that built and manages the rover, calls Seven Minutes of Terror due to the complexity of the landing process and the fact that they will be bystanders at that point. By the time they receive confirmation that the encapsulated rover has hit the top of the martian atmosphere it would have already landed, or crashed on the martian surface. It will take over 11 minutes for signals to reach us from Mars that day.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Delta of ancient river that flowed into a lake in the Jezero crater. This is a false color imaging highlighting mineral types. Credit NASA.
Mars Perseverance Rover’s planned landing ellipse partially overlapping the dried up river delta. Credit: NASA/JPL.
Mars 2020 Rover “Perseverance” destined for the martian crater Jezero.
11/20/2020 – Ephemeris – Martian Trojan asteroid may have come from our Moon
This is Ephemeris for Friday, November 20th. Today the Sun will be up for 9 hours and 22 minutes, setting at 5:09, and it will rise tomorrow at 7:48. The Moon, 1 day before first quarter, will set at 10:39 this evening.
The way gravity works there are several gravitational sweet spots called Lagrangian points between orbital bodies. Two of those points, 60 degrees ahead of and behind a planet in its orbit, are called L4 and L5. Bodies at these points are called Trojan asteroids. Because the first ones found in Jupiter’s orbit were named after warriors of the Trojan War. What was discovered recently was that one of the planet Mars’ L5 Trojans is not like the others. It has a different composition as analyzed by a spectrograph. It reflects light like the Earth’s Moon, while the others appear to have come from Mars itself. Perhaps an ejected piece of the Moon made it out to Mars orbit. We know small meteoroids can make it planet to planet, maybe huge chunks can make it too.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars and its Trojan asteroids including 101429 the asteroid that is spectroscopicly like the Moon. The other Trojans appear to have come from Mars itself. I tend to be a stickler for image accuracy: The Mars image is upside down and reversed, while the rest of the diagram is essentially correct other than being way out of scale. Credit Armagh Observatory and Planetarium (AOP) in Northern Ireland.
10/06/2020 – Ephemeris – Mars is closest today, also the Draconid meteors are at peak
This is Ephemeris for Tuesday, October 6th. Today the Sun will be up for 11 hours and 25 minutes, setting at 7:13, and it will rise tomorrow at 7:48. The Moon, 3 days before last quarter, will rise at 9:46 this evening.
Today Mars is at its closest to the Earth of this close approach, what astronomers call an apparition. The last close approach was at the end of July two years ago. It is still pretty small in telescopes. However being this close, 38.6 million miles (62.1 million kilometers) away, it is actually slightly brighter than Jupiter. Check them out. Mars is the bright orange tinged star in the east while Jupiter is in the south-southwest at 9 pm tonight. It’s still a week before Mars lines up with the Earth and Sun in opposition. Mars is closer now because it is moving away from the Sun in its orbit. We are at the peak of a weak meteor shower most years. It’s the Draconids, which appear to come from the head of Draco the dragon near the bright star Vega, nearly overhead in the evening.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addenda
Mars
Draconid Meteor Shower
08/03/2020 – Ephemeris – What is the Perseverance Rover going to do on Mars?
This is Ephemeris for Monday, August 3rd. Today the Sun will be up for 14 hours and 33 minutes, setting at 9:05, and it will rise tomorrow at 6:33. The Moon, at full today, will rise at 9:35 this evening.
The Mars Perseverance Rover looks a lot like the Curiosity Rover that landed on Mars in Gale Crater almost exactly 8 years ago (Earth years that is). It has more and better cameras, some different tools on its arm. It will have a laser like Curiosity. It can take core samples and store them in sealed tubes for later return to the Earth. It has an experimental helicopter drone named Ingenuity that must, like the rover be autonomous since it cannot be controlled in real-time from the Earth. The main mission this time is to look for signs of life in a spot we know water had flowed in the ancient past. The surface water and the life is long gone, but there might be signs that it might have been present in the distant past before Mars lost most of its atmosphere and water.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Artist rendition of the Mars 2020 “Endurance” Rover. Credit NASA.
Artist’s concept of the Mars Helicopter “Ingenuity”. Credit: NASA/JPL-Caltech.
Bob Moler's Ephemeris Blog 