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10/19/2021 – Ephemeris – Introducing the DART mission

October 19, 2021 Leave a comment

This is Bob Moler with Ephemeris for Tuesday, October 19th. Today the Sun will be up for 10 hours and 47 minutes, setting at 6:50, and it will rise tomorrow at 8:05. The Moon, 1 day before full, will set at 7:54 tomorrow morning.

Last Saturday morning, the Lucy mission to Jupiter’s Trojan Asteroids was launched. These asteroids are forever locked in Jupiter’s orbit and will never be a hazard to the Earth. Next month, NASA will hopefully launch a mission to a much closer asteroid Didymos, which is considered a potentially hazardous asteroid. The asteroid has a diameter of a bit less than a half mile (780 meters). It also has a satellite named Dimorphos, which has acquired the nickname Didymoon, 520 feet (160 meters) in diameter. The mission called DART for Double Asteroid Redirection Test will see how the impact of a spacecraft hitting the small Didymoon will affect its orbit around the larger asteroid.

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

The DART Mission

The Double Asteroid Redirection Test (DART) mission is NASA’s contribution to the international Asteroid Impact & Deflection Assessment (AIDA) program to determine the effectiveness of a spacecraft kinetic impact of an asteroid in altering its orbit. Credit: NASA.

10/15/2021 – Ephemeris – NASA mission to Trojan Asteroids

October 15, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, October 15th. Today the Sun will be up for 10 hours and 59 minutes, setting at 6:57, and it will rise tomorrow at 7:59. The Moon, 3 days past first quarter, will set at 3:25 tomorrow morning.

Tomorrow opens up a window to launch a satellite named Lucy to the Trojan asteroids of Jupiter. Lucy is named for a fossil of a human ancestor discovered in Africa. After launch, Lucy will make two gravitational assist passes of the Earth to get up enough velocity to reach Jupiter’s orbit and pass near Five asteroids in the leading L4 cloud of Trojans. Its orbit will take it back to the Earth, where another gravitational assist will send it to a double asteroid in the trailing Trojan group. On its way out it will pass close to a tiny main belt asteroid DonaldJohanson, named after the discoverer of the Lucy fossil. The mission will last 12 years. After that, Lucy will orbit between the Earth’s orbit and each of the Trojan swarms in turn.

Lucy is scheduled to launch on an Atlas V on Saturday, 16 October 2021 at 09:34 UT (5:34 a.m. EDT) from Cape Canaveral. If the launch can’t take place then, they have something like 22 more days in which they can get it launched.

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

Animation showing Jupiter and zTYrojan asteroids during one Jovian year

Animated GIF showing Jupiter and Trojan Asteroids during one Jovian year, which repeats. Credit: Astronomical Institute of CAS/Petr Scheirich.

Lucy misssion in Jupiter's rotating frame

The Lucy spacecraft orbits as seen in the rotating frame of Jupiter’s orbit. Lucy’s orbits are actually ellipses. (I wish they would take the stars out, they should appear as circular trails centered on the Sun from Jupiter’s rotating frame.) Click on the image to enlarge it. Credit: Southwest Research Institute.

 

10/14/2021 – Ephemeris – What is a Trojan Asteroid?

October 14, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, October 14th. Today the Sun will be up for 11 hours and 2 minutes, setting at 6:59, and it will rise tomorrow at 7:58. The Moon, 2 days past first quarter, will set at 2:13 tomorrow morning.

The Moon is near Jupiter tonight. On this Saturday, the 16th, the window opens up for the launch of NASA’s Lucy mission to Jupiter’s Trojan asteroids. More about the mission tomorrow, but what’s a Trojan asteroid? The Trojan asteroids are over 10,000 in number that lie in Jupiter’s orbit. One group, the Greeks, orbit around the L4 point 60 degrees ahead of Jupiter. The other, the Trojans orbit the L5 point 60 degrees behind Jupiter. Named after participants of the Trojan War, they are collectively named Trojan asteroids. Other planets, including the Earth, have Trojan asteroids. Trojan asteroids orbit the L4 and L5 gravitational equilibrium points in a planet’s orbit of the Sun, discovered by Joseph-Louis Lagrange in 1772. The first Trojan asteroid, was named Achilles after a warrior in the Trojan War, and was discovered in 1906. As new asteroids were found in these special positions, they were also given names from Homer’s Iliad.

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

Jupiter's Trojan Asteroids

The two “camps” of Jupiter’s Trojan Asteroids. The Greek camp at L4 and the Trojan camp at L5. Credit Astronomy.com/Roen Kelly.

Other planets have Trojan Asteroids in their orbits. Earth has one, Mars has four, Uranus has two, Neptune has 28.  These are not the final numbers, just what has been found so far. Apparently, Venus has a temporary one. When the term Trojan Asteroids is used without reference to a planet, they are assumed to belong to Jupiter.

10/04/2021 – Ephemeris – Why we can’t talk to the Perseverance rover on Mars right now

October 4, 2021 Comments off

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.

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

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.

09/16/2021 – Ephemeris – How safe is the Space Launch System (SLS) compared to the Space Shuttle?

September 16, 2021 Comments off

This is Ephemeris for Thursday, September 16th. Today the Sun will be up for 12 hours and 27 minutes, setting at 7:51, and it will rise tomorrow at 7:24. The Moon, 3 days past first quarter, will set at 3:10 tomorrow morning.

Tonight, the planet Saturn will appear above the bright gibbous Moon. It might be a bit hard to spot.

The big NASA moon rocket, the Space Launch System or SLS, borrowed a lot of features from the Space Shuttle. Is it any safer? The answer is yes. The Space Shuttle had no abort system for a catastrophic failure, as we saw with the Challenger accident in 1986. However, even though the SLS uses the same type solid rocket boosters that failed Challenger, the Crew in the Orion capsule is on top of the rocket with an escape system to rocket them away from an exploding core stage. With the Orion capsule, the escape tower will be jettisoned at some point before reaching orbit, possibly making escape impossible in the latter stage of powered flight. Both SpaceX’s Dragon and Boeing’s Starliner have escape rockets built in for the entire flight.

Addendum

Shuttle-SLS comparisons

Shuttle-SLS comparisons. Note that this image is 10 years old. The center core stage will, like the external tank on the shuttle, remain unpainted. So far, the cargo version of the is still in the design stage. The Multipurpose Crew Vehicle is now called the Orion Spacecraft. Credit: How Stuff Works.

09/14/2021 – Ephemeris – Lack of spacesuits just one of Artemis problems of getting humans back to the Moon

September 14, 2021 Comments off

This is Ephemeris for Tuesday, September 14th. Today the Sun will be up for 12 hours and 33 minutes, setting at 7:54, and it will rise tomorrow at 7:21. The Moon, 1 day past first quarter, will set at 12:53 tomorrow morning.

The bright gibbous Moon is a feast for binoculars or a telescope. However, the speed-up plan to land crews on the Moon in 2024 proposed by the former President is not appearing to pan out. One major item is space suits, which must be more rugged and impervious to the Lunar regolith, or soil, whose grains are tiny, angular and sharp, and get into everything, and can destroy spacesuit joints. NASA has been working on them for 14 years, and by itself could cost a billion dollars. They might be ready by 2025. Besides delays to the SLS rocket, the contract with SpaceX to furnish a lunar lander is now tied up in litigation by one of the contract losers. NASA’s trying to land humans on the Moon on one half of one percent of the Federal budget, plus do everything else it does.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Prototype lunar spacesuit

Prototype lunar spacesuit. xEMU stands for Exploration Extravehicular Activity Mobility Unit. Of course. This uncredited image is from slashgear.com in 2019, so I wouldn’t believe the date. These xEMU suits may eventually cost a billion dollars to develop and produce. Click on the image to enlarge it.

08/16/2021 – Ephemeris – The first Artemis mission (maybe) – CAPSTONE

August 16, 2021 Comments off

This is Ephemeris for Monday, August 16th. Today the Sun will be up for 13 hours and 59 minutes, setting at 8:46, and it will rise tomorrow at 6:47. The Moon, 1 day past first quarter, will set at 1:13 tomorrow morning.

Tonight’s Moon is a great one to view with a small telescope. Speaking of the Moon, a company called Rocket Lab will be launching the first Artemis program mission, later this year, in preparation to land crews back on the Moon. They are launching a small CubeSat to orbit the Moon in a Near Rectilinear Halo Orbit which always faces the Earth and never goes behind the Moon. To test whether all the mathematical calculations for the orbit actually work in real life. The satellite is called CAPSTONE (another tortured NASA acronym*). It will be launched from New Zealand, Rocket Lab’s main launch site first into a polar orbit before heading to the lunar orbit, taking several months to get there.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

* Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. Told ya. Cislunar space is a spherical volume of space centered on the Earth, whose radius is the Moon’s distance. Beyond that is interplanetary space.

Addendum

Rocket Lab had been planning to launch the CAPSTONE satellite from Wallops Island, Virginia, but approval was taking too long, so they moved the launch to their New Zealand launch site instead.

NASA CAPSTONE pathfinder for gateway orbit

NASA CAPSTONE* pathfinder for gateway orbit is to be launched late this year by Rocket Lab to prove out the near rectilinear orbit for the Lunar Gateway.

07/22/2021 – Ephemeris – Hubble’s trouble is fixed

July 22, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, July 22nd. Today the Sun will be up for 15 hours even, setting at 9:19, and it will rise tomorrow at 6:19. The Moon, 1 day before full, will set at 5:18 tomorrow morning.

Folks at NASA are breathing a sigh of relief. After a month when one of its computers failed in the Hubble Space Telescope, ground controllers were able to diagnose that the problem was actually in the computer and not somewhere else. They switched to a backup computer. This wasn’t the main computer, but the one that ran the instruments. Hubble resumed operations this past Sunday. Hubble’s more or less replacement, the James Webb Space Telescope is many years overdue to be launched, and is expected to be launched later this year by the European Space Agency from French Guiana, as their contribution to the project. The Webb telescope operates in the infrared, while Hubble operates mostly in visible light.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

The Hubble Space Telescope

The Hubble Space Telescope after its last servicing mission. Credit: NASA.

 

Full scale model of the JWST at Goddard Space Flight Center

Full scale model of the James Webb Space Telescope at Goddard Space Flight Center. Note its scale with the people in front of it.

06/17/2021 – Ephemeris – Congress approves more money for NASA’s lunar lander

June 17, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, June 17th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:56. The Moon, at first quarter tonight, will set at 2:18 tomorrow morning. | Tonight’s Moon will be almost exactly cut in half by the sunrise terminator, since the precise moment of first quarter will be at 11:54 this evening. Speaking of the Moon, Congress has approved NASA spending of 10 billion dollars over 5 years on the Human Lander System for the Artemis Moon program. This would allow more than one bidder to win the lander contract. SpaceX’s Lunar Starship was the only one to win a contract. NASA and Congress wanted two to win, but couldn’t afford more than SpaceX. Now comes the rub… Congress will have to appropriate the money out of the budget every year for this. The target date for the first landing is 2024, which I’m pretty sure is already out of reach.

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

First Quarter Moon with binoculars or low power telescope

First Quarter Moon with binoculars or low power telescope as it might appear tonight at 11 pm. Created using Stellarium.

Three Lunar Lander proposals

Three Lunar Lander proposals. Credit Dynetics, SpaceX, and Blue Origin. Credit NASA.

Also, SpaceX’s bid was the lowest by a wide margin. With the extra funds, it looks like Blue Origin will be the second successful bidder.

04/20/2021 – Ephemeris – SpaceX gets NASA contract for Human Landing System for the Artemis (Moon) Program

April 20, 2021 Comments off

This is Bob Moler with Ephemeris for Tuesday, April 20th. Today the Sun will be up for 13 hours and 44 minutes, setting at 8:34, and it will rise tomorrow at 6:47. The Moon, at first quarter today, will set at 4:24 tomorrow morning.

Late last week NASA announced that it had selected SpaceX to provide the Human Lander System for the Artemis program. That lander is the lunar variant of the Starship SpaceX is currently testing near Boca Chica, Texas, just north of the mouth of the Rio Grande. A Starship consists of two stages: a booster called Super Heavy and the Starship upper stage. The Super Heavy returns to the launch site, while the Starship must be refueled several times in orbit to be able to head on out to the Moon. The astronauts would be launched as planned in an Orion capsule with the Space Launch System, then transfer the astronauts to the Starship waiting in lunar orbit or from the Lunar Gateway also in lunar orbit for the trip down to the lunar surface.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

SpaceX Concept lunar Lander as of 04/16/2021
SpaceX’s updated concept of their Starship lunar lander as of 04/16/2021. Credit: SpaceX.

NASA’s Source Selection Document (the rationale for their selection): https://www.nasa.gov/sites/default/files/atoms/files/option-a-source-selection-statement-final.pdf