Seal

https://youtu.be/oYd2yd06m9I

https://nasa-2021.netlify.app

What is SEAL

SEAL, which stands for Super Emulator for Asteroid Lightcurve, is designed to show the rotation axis, the geometry, the albedo, and the orbital parameters of the asteroids effect the shape and the magnitude of light curve.

In addition, there are complete mathematical derivations, assumptions, explanations of various terms, and the light curve test on the website, which can provide students with learning and understanding of our light curve calculations. In the future, We believe this tool can be used in the educational field.

Why choose SEAL

SEAL has five features.

1. Users can upload their own model in the format of (.obj) and we have some default model from NASA 3D dataset.

2.Users can adjust various parameters flexibly, like the rotation axis, the geometry, the albedo, and the orbital parameters of the asteroids.

3.Our model can predict the apparent magnitude by phase integral With some physical assumptions.

4.Our interface can compare the light curve of your own simulation with the ALCDEF observation data.

5.Educational interactive test and mathematical derivations, assumptions, and explanations of various terms on our website.

SEAL is easy to use.

1.Select 3D model:

• 3D model from NASA database
• You can up load your 3D model in the format of (.obj)
• press next

2.Specify simulation parameter

• Select you Rotation model
• Set your Apparent magnitude prediction setting
• press next

3.Analyse light curve

• Enjoy your light curve
• You can compare it with the real observation data from ALCDEF data base

How we made SEAL

Methods

Physics model

Our simulation is based on a mathematical model derived from physics (Euler’s rotation equation) and physical assumptions, and our simulation results are in line with NASA open source real observation data.

Conditions:

1. Phase angle = 0 , solar opposition, perihelion

In order to simplify the problem, we set the phase angle = 0 ,the asteroid is in conditions of ideal solar opposition and it is at perihelion.

2. Asteroids are rigid and rough bodies

3. No external force (torque free) Angular momentum conservation

Rotation model 1 : Rotation around a fixed axis (special case: non-physical model)

We assume that the motion of asteroid is rotation around a fixed axis to simplify the setting and calculation. This setting is not the true rotation motion of the asteroid. Really rotating motion, the axis of rotation will also rotate, especially the rod-shaped or flatter (non-spherical) [Example link], but to calculate this requires numerical integration of the asteroid’s moment of inertia. Some of the moment of inertia distribution does not have an analytical solution, and it is necessary to solve the Euler equation numerically: Veritasium: The Bizarre Behavior of Rotating Bodies

Rotation model 2 : Symmetric top precession model (physical model)

In order to simplify the calculation complexity under the physical conditions, we assume such model based on the geometric configuration of the asteroid. This model is the simplest model that can simulate precession. Assuming that the object is axisymmetric, I1 = 12 is not equal to I3.

For Euler’s equations (rigid body dynamics) in our assumption

We get

Define

And we solve

After that we use ellipsoid (solid) of semiaxes a=b is not equal to c to approximate the moments of inertia of an asteroid which is

Apparent magnitude prediction model

We used 3D simulated cameras as telescopes to capture asteroids, and converted the white point value in the picture to equivalent diameter. By using condition 1 mentioned above and the Albedo provided by NASA’s LCDB database, we can calculate solar absolute magnitude using

Then use Eq.4 to calculate the apparent magnitude when looking at asteroids.

• d_bo is the distance between the body and the observer
• d_bs is the distance between the body and the Sun
• H is the absolute magnitude of Solar System bodies which is defined as the apparent magnitude that the object would have if it were one astronomical unit (AU) from both the Sun and the observer, and in conditions of ideal solar opposition (an arrangement that is impossible in practice).

Our prediction of apparent magnitude has a shift of ±0.5m compared to the actual ALCDEF data, but is accurate enough for a reference of light curve.

1. NASA 3D Model:https://nasa3d.arc.nasa.gov/search/asteroid
2. NASA Asteroid Shape Models:https://echo.jpl.nasa.gov/asteroids/shapes/shapes.html

Used as our model data for users to simulate Light Curve

1. LCDB data base:https://sbn.psi.edu/pds/resource/lc.html
2. ALCDEF data base:https://alcdef.org/index.php

Used as our Light Curve data for users to compare with emulate result

We are Team SEAL, and we made SEAL: Super Emulator for Asteroid Lightcurve. Our team members come from different fields, including Arts, Business, Computer Science, and Physics. We love to explore the unknown world and simplify complex knowledge for educational use. Through making visualized websites, we want more people to understand the science behind light curves.

We hope users can use this emulator and NASA open-source data to produce the time evolution relationship between the apparent magnitude of the 3D asteroid model and the free rigid body rotation Symmetric top precession, with 0 phase angle in solar opposition and perihelion.

Our emulation is based on a mathematical model derived from physics (Euler’s rotation equation) and physical assumptions. The results are in line with NASA’s open-source real observation data.

Users are allowed to upload their own model for emulation. Also, SEAL can produce the time evolution relationship between the apparent magnitude of the 3D asteroid model and the free rigid body rotation, and the simulation results in the Main belt and NEO conform to the ALCDEF observation data.

1.NASA 3D Model:https://nasa3d.arc.nasa.gov/search/asteroid

2.NASA Asteroid Shape Models:https://echo.jpl.nasa.gov/asteroids/shapes/shapes.html

3.LCDB data base:https://sbn.psi.edu/pds/resource/lc.html

4.ALCDEF data base:https://alcdef.org/index.php

5.three.js

6.echarts

7.Bootstrap

8.Vue

#Lightcurve , #Emulator, #LCDB, #ALCDEF, #education, #visualization, #Eular, #3D, #asteroid,#azure

This project has been submitted for consideration during the Judging process.