# Remote Sensing Hands-On Lesson using BepiColombo MPO¶

Virtual SPICE Training for BepiColombo, July 21-22, 2020

## Overview¶

In this lesson you will develop a series of simple programs that demonstrate the usage of SpiceyPy to compute a variety of different geometric quantities applicable to experiments carried out by a remote sensing instrument flown on an interplanetary spacecraft.

You may find it useful to consult the permuted index, the headers of various source modules, and several Required Reading documents available at the NAIF site.

## Initialise SPICE by importing SpiceyPy¶

For the following exercises, instead of loading the meta-kernel try to sort out the exact kernels that you need to load for the given execrcise and load them (unless indicated).

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## Time Conversion¶

Write a program that given a UTC time string, converts it to the following time systems and output formats:

- Ephemeris Time (ET) in seconds past J2000
- Calendar Ephemeris Time
- Spacecraft Clock Time (TIP: You will need to know the NAIF ID of MPO)

and displays the results. Use the program to convert "2020-OCT-15 03:57:49" UTC into these alternate systems.

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## Obtaining Target States and Positions - Venus Flyby¶

Write a program that given a UTC time string computes the following quantities at that epoch:

- The apparent state of Venus as seen from BepiColombo MPO in the J2000 frame, in kilometers and kilometers/second. This vector itself is not of any particular interest, but it is a useful intermediate quantity in some geometry calculations.

- The one-way light time between BepiColombo MPO and the apparent position of Earth, in seconds.

- The actual (geometric) distance between the Sun and Venus, in astronomical units.

and displays the results. Use the program to compute these quantities at "2020-OCT-15 03:57:49" UTC.

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## Spacecraft Orientation and Reference Frames¶

Write a program that given a UTC time string computes and displays the following at the epoch of interest:

- The angular separation between the apparent position of BepiColombo MMO as seen from BepiColombo MPO and the nominal instrument view direction.

The nominal instrument view direction is not provided by any kernel variable, but it is indicated in the BepiColombo MPO frame kernel.

Use the program to compute these quantities at the epoch "2027 JUN 11 20:50:00" UTC.

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## Computing Sub-s/c and Sub-solar Points on an Ellipsoid¶

Write a program that given a UTC time string computes the following quantities at that epoch:

- The apparent sub-observer point of MPO on Mercury, in the body fixed frame IAU_MERCURY, in kilometers.
- The apparent sub-solar point on MPO, as seen from MPO in the body fixed frame IAU_MERCURY, in kilometers.

For the computations use the ellipsoidal shape model:

    near point/ellipsoid

definition.

The program displays the results. Use the program to compute these quantities at "2027 JUN 11 20:10:00" UTC.

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## Intersecting Vectors with an Ellipsoid (fovint)¶

Write a program given an input UTC time string that computes the intersection of the MPO SERENA ELENA boresight and field of view (FOV) boundary vectors with the surface of Mercury.
The program presents each point of intersection as

- Planetocentric (latitudinal) coordinates in the IAU_MERCURY frame.

For each of the sensor FOV boundary and boresight vectors, if an intersection is found, the program displays the results of the above computations, otherwise it indicates no intersection exists.

At each point of intersection compute the following:

- Phase angle
- Solar incidence angle
- Emission angle

Use this program to compute values at "2027 JUN 11 20:10:00" UTC.

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## Extra Credit: Lessons with WGC¶

Try to reproduce all the previous calculations with WebGeocalc. You will need to load the appropriate meta-kernel: "SPICE CLASS -- BepiColombo Remote Sensing Lesson Kernels"