New Horizons and Ultima Thule

Just after midnight on January 1st, the New Horizons spacecraft will have its close encounter with the Kuiper Belt object Ultima Thule, also known as (486958) 2014 MU69. Since New Horizons flew by Pluto in July 2015 it has been preparing for this moment. Ultima Thule wasn’t even targeted until after the Pluto encounter was over, and it was only discovered in 2014. 

New Horizons spacecraft

Of course, the next thing is simulating the encounter in Starry Night. The first problem here is that the mission path provided for New Horizons in Starry Night doesn’t extend to the present day. However, the JPL HORIZONS service can provide updated state vectors, which I have put into the attached file New Horizons.xyz.

To get the updated mission path of New Horizons into your SciDome, download this zip, open it, and copy “New Horizons.xyz” into this folder on your Preflight computer running SciDome Version 7:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\Space Missions

This is a networked folder that exists on both Preflight and Renderbox computers, so the file only needs to be in one place in order to be accessible in both computers. If there is no “Space Missions” subfolder of this SkyData folder, you may have to create it. Although there will then be more than one version of the New Horizons file on your system, this one will take precedence.

Ultima Thule imagery captured by New Horizons

Next, we have to add Ultima Thule to Starry Night. I find the best way to do this is to right-click on the Sun and in the details window that pops up, select ‘New Asteroid…’ In the ‘Asteroid: Untitled’ window that pops up, enter the following data, which comes from the Minor Planet Center at Harvard:

Name: Ultima Thule
Mean Distance: 44.581400  
Eccentricity: 0.041725   
Inclination: 2.4512  
Ascending Node: 158.9977  
Arg of Pericentre: 174.4177  
Mean Anomaly: 316.5508  
Epoch: 2458600.5

Exit this window and answer the prompt, ‘Do you want to save changes…?’ with yes. The next time you quit Starry Night, this new object will be saved into a file called “User Planets.ssd” that lives on your Preflight computer, but is not automatically networked to the Renderbox. In order to get it to live on the Renderbox, you have to find “User Planets.ssd” and copy it into part of the Sky Data folder we looked at above.

Locate ‘User Planets.ssd’ in the following folder:

C:\Users\SPITZ\AppData\Local\Simulation Curriculum\Starry Night Prefs\Preflight\

Verify that this file was last modified on the date you are doing this work. 

The destination the file should be copied to is:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\

If there is an older version of ‘User Planets.ssd’ in the destination, better save it to a safe location, just in case.

The Ultima Thule encounter could be a strange one. Pluto is about as big as the United States, from the 49th parallel to the Rio Grande, but Ultima Thule is only about as big as Nantucket Sound. Its shape has been worked out from occultations, and it looks elongated, not round. You can get more data about the mission to share from this blog entry from Emily Lakdawalla at the Planetary Society.

You can run a simulation of the encounter on your phone with the free Pluto Safari app from Simulation Curriculum, our partners in developing Starry Night Dome and The Layered Earth Dome for SciDome planetariums.

Simulating Apollo 8 on SciDome

Tomorrow, Friday, will be the 50th anniversary of the launch of Apollo 8, the first crewed space flight to orbit the Moon. You can simulate Apollo 8, and the other eight Apollo missions that went to the Moon, on your SciDome.

Apollo 8 mission patch, showing the “figure 8” path the spacecraft travelled from the Earth to the Moon

First, make sure that ‘Space Missions’ are checked to be visible in your View Options pane. If you type in ‘Apollo’ in the Starry Night search engine pane, each mission will come up, and you can break each one down by “Mission Path segments” that each describe a phase of flight, and look at the Command Module and Lunar Module separately at relevant points.

These missions can only be seen when Starry Night is displaying the right time between 1968 and 1972, which you can get by right-clicking on the mission you want and selecting “Set Time to Mission Event…” and picking “Launch”, for example. The best way to see the mission path of Apollo is to be looking at it from well above the Earth’s surface, with ‘Hover as Earth Rotates’ set so that the Earth’s surface can rotate underneath you and the fixed stars stay fixed on the dome.

Apollo 8 follows a curving path out from the Earth to the Moon, orbits around the Moon ten times, and then returns to the Earth. The different mission path segments are different colors. 

You can see that the spacecraft orbits around the Moon from lunar west to lunar east. However, when we look up at Apollo’s path around the Moon it appears to be opposite the path that spacecraft orbit the Earth, even though everything launched from Cape Canaveral also goes towards the east. The Apollo spacecraft were launched into a figure-eight trajectory, so the “patching of conics” that reverses the frame of reference is like when two people shake hands on their right side. From one person’s point of view the other person is shaking their left hand, even though both participants are using their right.

The Apollo spacecraft and the Saturn V rocket are rendered in 3D in Starry Night if you go to them and look at them up close. The Apollo 8 spacecraft is pointed at the Earth by default.

Apollo 8 “Earthrise” photo

The famous “Earthrise” photo was taken at the beginning of the fourth orbit, on December 24th, 1968, at about 16:25 Universal Time, as shown in SciDome. There is some question of which of the three astronauts – Commander Frank Borman, Command Module Pilot Jim Lovell, or “Lunar Module” Pilot Bill Anders – took the photo, and the question was resolved by Apollo historian Andrew Chaikin, who recounts his investigations in Smithsonian Magazine.

In Starry Night Preflight’s ‘SkyGuide’ pane there is a section on the Apollo missions, and Apollo 8 has 13 sub-headings that go into phases of flight like the Earthrise photo in some detail. Each subheading calls up a Starry Night application favourite scene that describes that phase of flight, with some text and images that appear in the SkyGuide pane.

Simulating Juno’s Buzz by the Great Red Spot

Great Red Spot cloud detail from Juno’s extreme close approach. Credit : NASA / SwRI / MSSS / Gerald Eichstädt / Seán Doran © cc nc sa

One of the astronomical highlights of last week was the pictures returned by the Juno spacecraft orbiting Jupiter when it zipped over the Great Red Spot at an extremely low altitude (8000 km.) Although the JunoCam camera on this mission was an afterthought for public outreach purposes and not a research experiment, the camera has returned some data that can be amazing when processed, and shows no signs of stopping yet, despite Jupiter’s harsh radiation environment.

To simulate this mission in Starry Night Version 7 on a Spitz SciDome planetarium, a couple of changes need to be made, even with recent updates. But with those changes made, you can simulate this flypast in Starry Night, and also think about using some of the real camera images from Juno on your dome as slides with ATM-4.

Firstly, we need to update the Space Missions file Juno.xyz. Starry Night V7 may already have a version of the mission path, but that is the *planned* mission. An anomaly in Juno’s rocket engine led to a revised mission plan with a different path. The original path does not include a periapsis over the Great Red Spot on the date in question, July 10th. To update the mission path, download this zipped folder, unzip it, and move the contained file Juno.xyz to the following location:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\Space Missions\Juno.xyz

This change is only made in one networked location to affect both computers, to avoid tediously installing it on Preflight and Renderbox in two steps. Files added to the “ProgramData” Sky Data folder will override files with the same names added to the old-fashioned Sky Data folder in the folder “Program Files (x86)”. The “ProgramData” structure exists so that V7 users no longer need to tediously make changes to Program Files on either computer.

Secondly, the position of the Great Red Spot needs to be updated. Jupiter is not a solid body, and the Great Red Spot has a tendency to drift, and its drift rate has a tendency to change, generating an accumulating error. So it’s not practical to just use the GRS as the index for the fixed period of rotation of Jupiter that is mapped out by the surface texture in Starry Night. The value of the drift is currently about +5° per month, and the current value of the drift is about 271° in Jupiter System II longitude. (Last week I was using a value of 269° and that also came out pretty good: 269° represents the value during the Juno encounter.)

To edit the value in Starry Night V7 for SciDome, locate the following file and open it using Wordpad (not Notepad:)

C:\Program Files (x86)\Starry Night Preflight\Sky Data\JupiterGRS.txt

You may recognize that the code inside is a little odd: Double slashes in odd places. If you are familiar with the coding, these slashes take on added significance. They should each represent the beginning of a new line of code that should be ignored by the program.

The only part of the file that is read by the program is the line that does not begin with two slashes. Please edit the file if necessary so the text is as follows, and the value is updated:

// Enter the mean longitude of the Great Red Spot on the following line. Visit
// the Starry Night Pro website at http://www.starrynightpro.com to get the
// latest value.
269.0

Then save the file into the ProgramData folder as follows, in a single step:

C:\ProgramData\Simulation Curriculum\Starry Night Prefs\Sky Data\JupiterGRS.txt

Once again, saving in this location means it’s not necessary to save changes on the other computer as well.

Artist’s rendering of the Juno spacecraft.

There is a 3D model of the Juno spacecraft in SciDome version 7, so you ought to be able to simulate its swooping down on the Great Red Spot in different ways: A long view of Jupiter with the Juno “Mission Path” turned on and the spacecraft labelled as a dot, or also flying alongside the spacecraft 3D model as the GRS looms on the limb of Jupiter overhead.

If you are using Starry Night Version 6 for Scidome, you can still place the attached Juno.xyz in the Space Missions folder of the original Sky Data folder on both computers and chart the updated path, but there is no 3D model of the spacecraft available. There is a separate 3D model that represents the asteroid (3) Juno, and they could get mixed up.

Because the GRS will continue to drift, you may wish to return to make subsequent edits to JupiterGRS.txt. The drift currently accumulates +5° per month, but because the drift rate can change, I recommend doing one of two things:

1) Now that you have the Juno simulation of what will probably be the best and closest images of the Great Red Spot for our lifetime, don’t make any further changes to the GRS value. Further edits to the drifting value will start to “break” the position of the GRS during the Juno flyby on July 10th, if you have built an ATM-4 automation out of it.

2) Continue to update the GRS position to represent reality based on observations, not predictions to avoid accumulating drift error. The current System II longitude of the GRS is kept up to date in a couple of places on the Internet, such as CalSky.

It is possible that Juno will have another encounter with the Great Red Spot on one of its remaining orbits, but the period of its orbit around Jupiter is 53 days. In multiples of 53 days the GRS position value will change by multiples of 9°, with some accumulation of error, and the orbital period of the spacecraft is not an integer multiple of the rotation period of Jupiter. Let’s wait and see.