VEX Science Planning Options

[cndwrld]

Hello-

I wasn't sure how most people would like to see stuff posted. Or if this would interest many people. But in the interests of putting out more information, I created this topic as a place to put information on Venus Express science planning.

If you have any ideas about this, let me know.

Cheers-

Don Merritt

[cndwrld]

Science Planning Overview

The VEX science planning is done in three phases: Long term (covering nominal mission, extended mission, etc.); medium term (months in advance, one month at a time, submitted early to allow for review/analysis by the flight control team at ESOC/Darmstadt); short term (final operational files, provided one week prior to execution on the spacecraft, ideally the same as the medium term files). Each Medium Term Plan (MTP) covers 28 days, broken into four seven day periods. When the operational files are provided in the short term cycle a week before execution, the flight control team then typically breaks the files into smaller pieces for upload; the on-board command buffer being sized to hold about two days of commands, each day will have today's and tomorrow's commands uploaded.

The science observations are broken down into "cases", which are rough templates based upon either the instrument doing the observation, the location in the orbit (distance from cloud tops effecting data resolution) or other spacecraft pointing.

Note that the orbit has an inclination of 90 degrees (polar), and pericenter is at about 80 degrees north:
Pericentre altitude (km) 250
Apocentre altitude (km) 66 000
Period (h) 24
Inclination (°) ~90
Pericentre latitude (°) 80


The basic science observation cases are:
Case 1: observations near pericenter, typically from Venus Pericenter (VPER) - 00:47 (47 minutes), until VPER + 00:47. High spatial resolution spectroscopic and imaging of northern hemisphere, plasma and magnetic field studies (although these are also done at all points in the orbit when spacecraft operations and data volumes allow).

Case 2: Off-pericenter, ascending branch, typically between VPER-10:00 and VPER-01:00. Mainly used by VMC camera and VIRTIS imaging spectrometer, for studying upper atmospheric dynamics.

Case 3: Apocenter observations, typically between VPER-14:00 and VPER-10:00. Global spectrographic imaging of south pole using the VIRTIS imaging spectrometer.

Case 4: Radio Science Bistatic Radar observations, where the spacecraft transmitter is directed at surface features and the reflection is detected on Earth. VeRA experiment only. Used to study surface properties. Can only be done when spacecraft/Venus object of interest/Earth line up.

Case 5: Stellar occultations by SPICAV instrument, following a star as the spacecraft goes behind the planet and re-emerges from behind the planet (relative to the star used), useful for upper atmosphere studies.

Case 6: Solar Occultation using the SPICAV/SOIR experiment, tracking the Sun as it is occulted by the planet, to study the upper atmosphere.

Case 7: Limb observations, mainly for SPICAV but also by VMC camera and VIRTIS, to study atmospheric composition and structure.

Case 8: Earth radio occultaions by VeRA radio science experiment to study fine structure of the atmosphere. Or at least to capture the data, to be studied some day.

Case 9: VeRA sounding of solar corona, when near Superior Conjunction with the Sun directly (or nearly directly) between spacecraft/Venus and the Earth. Limited use due to geometry required.

Case 10: Venus Gravity anomaly studies using VeRA radio Science. Not yet done due to geometry, thermal constraints.

If I knew how to get drawings in here, it would be more clear with pictures.

Cheers-

Don Merritt

Some references:
http://en.wikipedia.org/wiki/Venus_Express
http://www.esa.int/SPECIALS/Venus_Express/