Thanks for installing the Aurora Forecast 3D - Satellite. Hopefully, you will enjoy it and make use of it as a tool to track down the aurora. It renders the Earth in 3D with rotation and scaling at your fingertips. You can select Location and make your own Station anywhere on the planet. The Sun illuminates the globe as it updates in near real-time (1s). The forecasts are up to +4 hours ahead in time. They are updated every 15 minutes when the app is active and connected to internet.

The Skyview module shows a fish-eye view of the sky including the auroral ovals, satellites, planets and stars as seen from any ground point location.

Below is a short description on how to use the app.

The above screen shot is marked with text labels. The circular green transparent belt is the aurora oval ^[1,2]. Two colored polygons mark the positions of your Station (red) and the Ground-track point (orange). The optical horizon for 110 km of altitude is visualized as a transparent disk centered at the track point.

City lights are included based on data from the NASA/Goddard Space Flight Center^[3]. In addition, an aurora compass is shown in the top left corner and 8 x speed buttons are grouped to the right. The auroral activity is presented using a speedometer layout.

The Aurora Compass shows where the auroral oval is located as you look up at the sky from the center Ground-track point.

This point is marked with an orange circular polygon on the Globe. Tap it, if you want to mark it as "My location". The latitude and longitude are shown at the top of the screen. You can rotate the Globe to move to any desired position.

The oval all-sky cover is shown in percentage in the center of the compass. The orange star marks the position of the Sun in the compass. The Moon symbol is explaned below according to phase and age. These will only appear if they are within the field of view as seen from the Ground-track point.

The above symbols represent the Moon as observed from the northern hemisphere. In the southern hemisphere these moon symbols are swapped horizontally (mirrored).

The speedometer is used to visualize the auroral activity based on the Kp-index (0 - 9).

The index is a measure on how disturbed the planetary geomagnetic field is. It is directly related to auroral activity. The predicted Kp values (0, +1 or +4 hours) are estimated by the Space Weather Prediction Centre (NOAA-SWPC) using satellites that monitor the Sun.

Hint: You can set your own Kp-index by tapping the color scale on the wheel.

Aurora sky view probability as seen from the Ground-track point.

+0 hour Nowcast.

+1 hour Forecast.

+4 hours Forecast.

Toggle Day/Night ON/OFF.

Return to Station point.

Zoom RESET.

Zoom IN.

Zoom OUT.

Share Screenshot (Android and iOS)

Repeat news ticker - text line

Track Satellite position

The positions ^[4] and apparent size of the inner planets are scaled in 3D according to the size of the Earth, but the distance is for artistic reasons not correct. It is in reality much further away. The apparent distance of the Sun is scaled down 500 times. The outer planets are scaled down and located at infinity close to the stars. Textures of the Earth, the Sun and the Moon are downloaded from the internet ^[5,6].

The stars in the 3D viewport are from the Tycho catalog sky map by NASA ^[7] version 2.0. The map is projected using a cylindrical-equidistant transform that is wrapped to a outer celestrial sphere.

The red cross in the star map marks the position of Zero Right Ascension (RA) and Declination (DEC).

It is known as the First Point of Aries and is the location of the vernal equinox

The positions of the satellites are calculated by code ^[8] based on Two-Line Element (TLE) sets provided by the Center for Space Standards and Innovation (CSSi). Each set groups the satellites according to mission objectives like communication, navigation or pure scientific purpose etc. The TLE sets are updated automatically every 72 hours. You may force an updated TLE by using the "Refresh" button in the "Edit" menu.

Default satellite is the International Space Station (ISS). Hit the "Track" button in the "Setup" menu to locate the current position of it.

The Skyview module is activated by tapping the Aurora Compass in the 3D viewport. The Bright Star Catalogue edition 5 (BSC5) ^[9] is used to plot stars brighter than magnitude 4. A red circle identifies the selected object to track in azimuth (AZ) and elevation (EL).

You can make your own station or modify the pre-defined station list that came with the app. Note that it is not possible to delete "My location". It is hooked up to the output of the location sensor. Go to the "Setup" menu and open the Editor by clicking on the "Edit" button.

STEP 1
First, enter only letters for the station name. All numbers are float using the dot "." as decimal separator. Latitude must be entered as decimal degrees and is positive to the North and negative to the South. Correspondingly, longitude is positive to the East and negative to the West. The altitude is in units of meters (m).

STEP 2
Secondly, test the input values by using the "Check" button. If this operation ends with an "OK", then proceed to the third and final step.

STEP 3
The station is added to the end of the list if you hit the "Add" button. It will be deleted from the list if you use the "Delete" button. If you simply want to modify or update the station, then use the "Update" button.

Hint: Use the location sensor to obtain the position you are located at. Then change the name of "My Location" and simply add it as a new station.

STEP 4
Finally, save your new station list and default settings for the app by clicking the "Save" button in the "Setup" menu.

If a geomagnetic storm occurs (Kp>5), then you will receive an alert message. It pops up as a vertical aligned text line to the left in the 3D viewport. The alerts are grouped according to the definition provided by NOAA-SWPC.

Minor

5

1700

Moderate

6

600

Strong

7

200

Severe

8

100

Extreme

9

4

The frequency is number of events per solar cycle (11 years).

Active sunspot Region

Coronal Hole

Co-rotating Interaction Region

Coronal Mass Ejection

Disappearing Solar Filament

Heliospheric Current Sheet

High Speed Stream

Interplanetary Magnetic Field

Lagrangian point 1

Sudden Impulse

Stream Interaction Region

Solar Proton Event

Solar Sector Boundary Crossing

In addition to the above short term forecasts, three day alerts from NOAA-SWPC are shown as sliding text - news ticker. Click bottom left button to repeat message. Note that any aurora occurrence of the 3-day alerts depends highly on the solar wind IMF configuration, and might not kick in. Enable the "Alerts" checkbox in the "Edit" menu to use this option (Default is ON).

First, locate a city or an airport above the Arctic Circle. Secondly, remember that it has to be dark. The Sun needs to be ~10 degrees below the horizon. Otherwise, the aurora will be drowned in solar light. In the northern hemisphere, this means late autumn to early spring with best viewing conditions during the late afternoon and into the night. At Svalbard we see it all day during mid-winter. Thirdly, I would recommend a location where there is stable in-land climate during the winter. For example, Fairbanks in Alaska or Alta in Norway are excellent locations. Another option is to take a boat trip and hunt for clear skies.

For most people on Earth, you will have time to eat dinner. Then check your local weather forecast for clear skies. Start the app and locate the auroral oval. If you have a clear view of the oval above your head, seen in the Aurora Compass, then you have up to 75% chance to see the aurora. Happy hunting!

There are two animated sequences available. The first one is started and stopped by double click the top right button in the 3D viewport. It starts a loop that visits every station in your list every 5 seconds for all forecasts. The animation starts with the text "...". End it by double click the button once more. It will then respond with ".". The second animation is enabled correspondingly in the Skyview module. It displays the daily sequence in epochs of 15 minutes for the current selected Ground-track point.

The app is setup to Nowcast and Forecast in Universal Time (UT). If you want to change date to study the ovals at any other time epoch, then enter the 'Edit' menu. Enable the 'Prediction' checkbox and enter the date selection menu. Do the same for the 'Update' menu to set the clock. You can now also change the Kp-index by tapping the color wheel in the Kp-indicator.

Note that the app will still work if your device is not connected to the internet. But the Kp index and the alerts are then not updated. The help file is locally installed and do not require a network connection. Default input values and locations can be restored. Close the app and delete the cash / data used by the app. This is done in your phone's settings. You can now restart with default settings.

A warning sign appears when the forecasts are not valid or when there is no internet.

[1] Sigernes F., M. Dyrland, P. Brekke, S. Chernouss, D.A. Lorentzen, K. Oksavik, and C.S. Deehr, Two methods to forecast auroral displays, Journal of Space Weather and Space Climate (SWSC), Vol. 1, No. 1, A03, DOI:10.1051/swsc/2011003, 2011.

[2] Starkov G. V., Mathematical model of the auroral boundaries, Geomagnetism and Aeronomy, 34 (3), 331-336, 1994.

[3] The Visible Earth catalog, http://visibleearth.nasa.gov, NASA/Goddard Space Flight Center, April-October, 2012.

[4] P. Schlyter, How to compute planetary positions, http://stjarnhimlen.se, Stockholm, Sweden, 1979.

[5] T. Patterson, Natural Earth III - Texture Maps, www.shadedrelief.com, October 1, 2016.

[6] Nexus - Planet Textures, www.solarsystemscope.com, January 4, 2013.

[7] Bridgman, T. and Wright, E., The Tycho Catalog Sky map- Version 2.0, NASA/Goddard Space Flight Center Scientific Visualization Studio, http://svs.gsfc.nasa.gov, January 26, 2009.

[8] Vallado, David A., Paul Crawford, Richard Hujsak, and T.S. Kelso, Revisiting Spacetrack Report #3, AIAA/AAS-2006-6753, https://celestrak.com, 2006.

[9] Hoffleit, D. and Warren, Jr., W.H., The Bright Star Catalog, 5th Revised Edition (Preliminary Version), Astronomical Data Center, NSSDC/ADC, 1991.

Copyright
The application is made by F. Sigernes (email: freds@unis.no), Longyearbyen, Svalbard, Norway (2016). It is considered licensed as fredware.