Mission Overview
================
Mars Express was the first flexible mission of the revised long-term
ESA Science Programme Horizons 2000 and was launched to the planet
Mars from Baikonur (Kazakhstan) on June 2nd 2003. A Soyuz-Fregat
launcher injected the Mars Express total mass of about 1200 kg into
Mars transfer orbit. Details about the mission launch sequence and
profile can be obtained from the Mission Plan [MEX-MMT-RP-0221] and
from the Consolidated Report on Mission Analysis (CREMA)
[MEX-ESC-RP-5500].

The mission consisted of (i) a 3-axis stabilized orbiter with a fixed
high-gain antenna and body-mounted instruments, and (ii) a lander
named BEAGLE-2, and was dedicated to the orbital and in-situ study of
the interior, subsurface, surface and atmosphere of the planet. After
ejection of a small lander on 18 December 2003 and Mars orbit
insertion (MOI) on 25 December 2003, the orbiter experiments began
the acquisition of scientific data from Mars and its environment in a
polar elliptical orbit.

The nominal mission lifetime for the orbiter was 687 days following
Mars orbit insertion, starting after a 5 months cruise. The nominal
science phase was extended (tbc) for another Martian year in order to
complement earlier observations and allow data relay communications
for various potential Mars landers up to 2008, provided that the
spacecraft resources permit it.

The Mars Express spacecraft represented the core of the mission,
being scientifically justified on its own by investigations such
as high- resolution imaging and mineralogical mapping of the
surface, radar sounding of the subsurface structure down to the
permafrost, precise determination of the atmospheric circulation
and composition, and study of the interaction of the atmosphere
with the interplanetary medium. The broad scientific objectives of
the orbiter payload are briefly listed thereafter and are given
more extensively in the experiment publications contained in ESA's
Special Publication Series. See [NEUKUM&JAUMANN2004],
[BIBRINGETAL2004], [PICARDIETAL2004], [FORMISANOETAL2004],
[BERTAUXETAL2004], [PAETZOLDETAL2004] and [PULLANETAL2004].

The Mars Express lander Beagle-2 was ejected towards the Mars
surface on 19 December 2003, six days before the orbiters capture
manoeuvre. The probe mass was limited to about 70 kg by the
mission constraints, which led to a landed mass of 32 kg. The
complete experimental package was weighed in approximately at 9kg.
The landers highly integrated scientific payload was supposed to
focus on finding whether there is convincing evidence for past
life on Mars or assessing if the conditions were ever suitable.
Following safe landing on Mars, this lander mission would have
conducted dedicated studies of the geology, mineralogy,
geochemistry, meteorology and exobiology of the immediate landing
site located in Isidis Planitia (90.74 deg E, 11.6 deg N), as well
as studies of the chemistry of the Martian atmosphere. Surface
operations were planned to last about 180 sols or Martian days (
about 6 months on Earth), see [SIMSETAL1999]. As no communication
could be established to the BEAGLE-2 lander, it was considered
lost in February 2004 after an extensive 'search'.

A nominal launch of Mars Express allowed the modify the orbit to a
'G3-ubeq100' orbit. The 'G3-ubeq100' orbit is an elliptical orbit,
starting with the sub-spacecraft point at pericentre at the equator
and a sun elevation of 60 degrees.
At the beginning of the mission, the pericentre moves southward with
a shift of 0.54 degree per day. At the same time the pericentre steps
towards the terminator which will be reached after about 4 months,
giving the optical instruments optimal observing conditions during
this initial period. Throughout this initial phase lasting until mid-
May 2004, the downlink rate will decrease from 114 kbit/s to
38 kbit/s.
After an orbit change manoeuvre on 06 May 2004 the pericentre
latitude motion is increased to guarantee a 50/50 balance between
dayside and nightside operations. With this manoeuvre, the apocentre
altitude is lowered from 14887 km to 13448 km, the orbital period
lowered from ~7.6 hours to 6.645 hours, and the pericentre latitude
drift slightly increased to 0.64 degree per day.
After 150 days, at the beginning of June 2004, the South pole region
was reached with the pericentre already behind the terminator.
Following, the pericentre moves northward with the Sun elevation
increasing. Thus, the optical instruments covered the Northern Mars
hemisphere under good illumination conditions from mid-September 2004
to March 2005.
During the next mission phase, lasting until July 2005, the
pericentre was again in the dark. It covered the North polar region
and moves southward.
Finally, throughout the last 4 months of the nominal mission, the
pericentre was back to daylight and moves from the equator to the
South pole, and the downlink rate reached its highest rate of 228
kbit/s. The osculating orbit elements for the eq100 orbit are listed
below:

Epoch 2004:1:13 - 15:56:0.096
Pericentre (rel. sphere of 3397.2 km) 279.29 km
Apocentre (rel. sphere) 11634.48 km
Semimajor axis 9354.09 km
Eccentricity 0.60696
Inclination 86.583
Right ascension of ascending node 228.774
Argument of pericentre 357.981
True anomaly -0.001


Mission Phases
==============
The mission phases are defined as:

(i) Pre-launch, Launch and Early Operations activities, including
(1) science observation planning;
(2) payload assembly, integration and testing;
(3) payload data processing software design, development and
testing;
(4) payload calibration;
(5) data archive definition and planning;
(6) launch campaign.

(ii) Near-Earth verification (EV) phase, including
(1) commissioning of the orbiter spacecraft;
(2) verification of the payload status;
(3) early commissioning of payload.

(iii) Interplanetary cruise (IC) phase
(1) payload checkouts
(2) trajectory corrections

(iv) Mars arrival and orbit insertion (MOI)
(1) Mars arrival preparation;
(2) lander ejection;
(3) orbit insertion;
(4) operational orbit reached and declared;
(5) no payload activities.

(v) Mars commissioning phase
(1) final instrument commissioning,
(2) first science results,
(3) change of orbital plane.

(vi) Routine phase;
Opportunities for dawn/dusk observations, mostly spectroscopy and
photometry. This phase continued into a low data rate phase (night
time; favorable for radar and spectrometers).
Then daylight time, and went into a higher data rate period
(medium illumination, zenith, then decreasing illumination
conditions).
Observational conditions were most favorable for the optical
imaging instruments at the end of the routine phase, when both
data downlink rate and Sun elevation are high.

(vii) MARSIS Deployment
The dates of the MARSIS antenna deployment is not known as of
writing this catalogue file.

(viii) Extended operations phase
A mission extension will be proposed in early 2005 to the Science
Programme Committee (SPC).

(ix) Post-mission phase (final data archival).


Science Subphases
=================
For the purpose of structuring further the payload operations
planning, the mission phases are further divided into science
subphases. The science subphases are defined according to operational
restrictions, the main operational restrictions being the downlink
rate and the Sun elevation.

The Mars Commissioning Phase and the Mars Routine Phase are therefore
divided into a number of science subphases using various combinations
of Sun elevations and available downlink bit rates.

The discrete downlink rates available throughout the nominal mission
are:
- 28 kbits/seconds
- 38 kbits/seconds
- 45 kbits/seconds
- 57 kbits/seconds
- 76 kbits/seconds
- 91 kbits/seconds
- 114 kbits/seconds
- 152 kbits/seconds
- 182 kbits/seconds
- 228 kbits/seconds

The adopted Sun elevation coding convention is as follows:
- HSE for High Sun Elevation (> 60 degrees)
- MSE for Medium Sun Elevation (between 20 and 60 degrees)
- LSE for Low Sun Elevation (between -15 and 20 degrees)
- NSE for Negative Sun Elevation (< -15 degrees)

The science subphase naming convention is as follows:
- Science Phase
- Sun Elevation Code
- Downlink Rate
- Science Subphase Repetition Number

The following tables gives the available Science Subphases:

NAME START END ORBITS BIT SUN
RATE ELE
----------------------------------------------------------
MC Phase 0 2003-12-30 - 2004-01-13 1 - 16
MC Phase 1 2004-01-13 - 2004-01-28 17 - 58 114 59
MC Phase 2 2004-01-28 - 2004-02-12 59 - 105 91 69
MC Phase 3 2004-02-12 - 2004-03-15 106 - 208 76 71
MC Phase 4 2004-03-15 - 2004-04-06 209 - 278 57 51
MC Phase 5 2004-04-06 - 2004-04-20 279 - 320 45 33
MC Phase 6 2004-04-20 - 2004-06-04 321 - 475 38 22

MR Phase 1 2004-06-05 - 2004-08-16 476 - 733 28 -13
MR Phase 2 2004-08-16 - 2004-10-16 734 - 951 28 -26
MR Phase 3 2004-10-16 - 2005-01-07 952 - 1250 28 16
MR Phase 4 2004-01-08 - 2005-03-05 1251 - 1454 45 63
MR Phase 5 2004-03-05 - 2005-03-24 1455 - 1522 76 16
MR Phase 6 2004-03-25 - 2005-07-15 1523 - 1915 91 0

The data rate is given in kbit per seconds and represents
the minimal data rate during the subphase.
The sun elevation is given in degrees and represents the
rate at the beginning of the subphase.

Detailed information on the science subphases can be found in
[MEX-EST-PL-13128].

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