All times for events on the spacecraft are given
as the time signal would be received on Earth in Pacific Daylight Time
(i.e. spacecraft event time plus one-way light time, which is approximately
10 minutes, 40 seconds). All operations events on Earth are in Pacific
Daylight Time. Pacific Daylight Time is Universal Time minus 7 hours.
June 30:
12 a.m.: Mars Pathfinder is approximately 1.3
million miles (2.0 million kilometers) from Mars, traveling at a velocity
of about 12,000 miles per hour (19,080 kilometers per hour) with respect
to Mars.
July 1:
12 a.m.: Mars Pathfinder is about 982,000 miles
(1.6 million kilometers) from Mars, traveling at a velocity of about 12,000
miles per hour (19,080 kilometers per hour) with respect to Mars.
July 2:
12 a.m.: Mars Pathfinder is about 695,000 miles
(1.1 million kilometers) from Mars, traveling at a speed of about 12,000
miles per hour (19,080 kilometers per hour) with respect to Mars.
July 3:
12 a.m.: Mars Pathfinder is about 409,000 miles
(658,000 kilometers) from Mars, traveling at a speed of about 12,000 miles
per hour (19,080 kilometers per hour) with respect to Mars.
July 4:
12 a.m.: Mars Pathfinder is about 121,000 miles
(195,000 kilometers) from Mars, traveling at a velocity of about 12,000
miles per hour (19,080 kilometers per hour) with respect to Mars.
9:32 a.m.: Cruise stage separation
10:02 a.m.: Pathfinder enters the upper atmosphere
of Mars at 16,600 miles per hour (26,460 kilometers per hour) and begins
the sequence of events that will land the spacecraft on the surface. From
this point on, the only likely signal from the spacecraft will be the carrier
wave, a single frequency radio wave. The shifting frequency of the carrier,
know as the Doppler shift, will provide an indication of the decelerations
occurring during entry and parachute deployment.
The spacecraft is also designed to send back a frequency-keyed signal following certain key events;
this signal is called a semaphore. The semaphore is very weak, and is not
expected to be received in real time. However, careful analysis after-the-fact
of the broad frequency spectrum recording of the radio signal will give
the operations team considerable information on how events unfolded during
the rapid descent to the surface.
Entry, descent and landing (EDL) takes approximately
4.5 minutes and follows the sequence below:
Spacecraft rapidly decelerates in the atmosphere using the heatshield
Parachute deploys
Heat shield separates
Lander releases from backshell, descends on bridle
Radar altimeter returns information on altitude
Airbags inflate
Rocket-assisted deceleration (RAD) engines fire
Bridle cable is cut
10:07 a.m.: Landing on surface of Mars in Ares
Vallis. Transmitter turned off shortly after landing to save power. After
touchdown, the following sequence will occur:
Lander bounces and rolls to a stop
Airbags deflate and are retracted up against the petals
Petals open
These events of the entry, descent and landing
phase will be complete between 11:32 a.m. and 12:33 p.m. PDT. A semaphore
signaling the end of this phase may be received via the lander's low-gain
antenna.
2 p.m.: Sunrise at the landing site.
Operations begin for Sol 1 (a Sol is a Mars day, or 24 hours, 40 minutes).
1:56-3:13 p.m.:
Transmitter is turned on, and
the spacecraft signals Earth through the low-gain antenna. This communications
session will contain telemetry from all engineering subsystems including
the rover, and the first science data about the atmosphere taken during
descent. Carrier is received at 1:55 p.m.; following ground processing,
actual first information will probably be received by flight controllers
at approximately 2:09 p.m.
Nominal Mission Scenario
If all subsystems are normal, the mission will
proceed on its "nominal" plan. In all likelihood, however, there
will some condition or conditions of the spacecraft that will be different
than the ideal case -- for example, an unusually tilted orientation of
the lander due to larger than anticipated rocks, or an airbag draping a
solar panel, or some damaged hardware due to a harder than expected landing.
At this point the mission team may enter a contingency mode where it uses
commands and prepared sequences to further evaluate the health of the lander
and improve its ability to continue the mission. Under such circumstances,
the highest priority will be to assure the safety of the spacecraft and
rover, and to insure enough power for operations and to recharge the battery.
Another possible contingency situation is loss of data due to a spacecraft
or ground problem that would require using one of two remaining downlink
sessions to retransmit data. Such a situation also will result in replanning
the rest of the first day's activities.
If the mission follows the nominal plan, the following events will occur:
3:20 p.m.:
The camera on the lander is released
and begins searching for the Sun. The high-gain communications antenna
is deployed and pointed toward Earth.
4:13-5 p.m.:
First high-gain antenna downlink
session. First engineering images of lander, airbags and the region around
the lander. The very first image frame will be of a small region including
part of the lander and an airbag. Assessment of these first images will
tell the operations team about the condition of the spacecraft, the airbags
and whether the rover ramps can be deployed. First color images of the
region around the rover petal will be sent.
Low-Gain Communications Scenario
Both the lander imager's Sun search and the high-gain
antenna deployment must be completed successfully for the images described
above to be received. If either activity is not completed fully, the team
will intentionally go to a less complex plan of events using the lander's
low-gain antenna. The low-gain antenna does not require knowledge of the
spacecraft orientation on Mars or active pointing to Earth. This is a likely
contingency scenario that has been well practiced and would proceed on
the following timeline (attempts to find the sun and point the high-gain
antenna at Earth would normally resume on Sol 2).
6:06-7:51 p.m.:
Low-gain antenna downlink session,
including compressed rover ramp deployment images (black-and-white with
80-to-1 compression). Approximately 12 images will be sent. The rover team
will evaluate feasibility of ramp deployment based on these images.
7-8:15 p.m.:
During this window, a decision will
be made to deploy one or both rover ramps and command the rover to stand
up. If more imaging is needed to make this decision, it will be requested
at this time.
8:44 p.m.:
If the decision is made to deploy
either or both ramps, this will occur at this time in the following sequence:
activate ramp deploy sequence; release the rover's alpha proton X-ray spectrometer
instrument; release the rover from its stowed position; deploy the rover
ramps. The rover will then stand up. A semaphore would be transmitted to
Earth indicating that the command was received to begin the sequence. In
this low-gain antenna scenario, this is the end of Sol 1 because no more
telemetry would be received. The downlink capability ends as the Earth
sets to about 30 degrees above the Mars horizon.
Nominal Mission Scenario
If, on the other hand, the high-gain antenna
is pointed toward Earth, the following timeline will be followed. It should
be remembered that unexpected events can occur at anytime which may change
this timeline. As always, the highest priority will be to assure the safety
of the spacecraft and rover, and to insure enough power for operations
and to recharge the battery.
5:40-5:55 p.m.:
Command conference to decide
whether to deploy the rover ramp.6 p.m.: Assuming that the rover and project
team judge it safe, the ramp deployment sequence will begin at about this
time.
6:55-7:57 p.m.:
Second high-gain antenna downlink
with rover deploy images (black-and-white), showing the ramps deployed.
Engineering data, more detailed entry and weather data will be sent. Part
of a black-and-white panorama image transmitted to Earth.
7:30-8:50 p.m.:
Rover and project teams decide
whether to deploy rover, based on the position of the ramp(s) on the surface
and the expected ability of the rover to safely traverse the area immediately
off the end of the ramp(s).
8:58 p.m.:
If all conditions are judged acceptable,
the rover deploy sequence will be activated and the rover will drive off
the lander petal, down a ramp (either forward or backward), and roll out
onto the surface of Mars. The alpha proton X-ray spectrometer will be lowered
onto the soil to prepare for deployment.
9:24-10:26 p.m.:
Third high-gain antenna downlink
session. Images should show the rover on the surface of Mars. Based on
this imaging, the rover team may decide to deploy the alpha proton X-ray
spectrometer. Other images may include a black-and-white 360-degree panorama
of the landing site.
10:30 p.m.:
Sun sets at landing site, rover goes
to sleep. If the alpha proton X-ray spectrometer was deployed, it will
be taking measurements of rock and soil composition and storing data all
night long.
July 5: Low-Gain Communications Scenario
Resuming this scenario in the event that the
high-gain antenna is not deployed on the first day:
Night of Sol 1:
The flight team processes images
of radiometric calibration target, and develops an estimate of the Sun's
position. This information may then be used to estimate the lander orientation
on the surface and allow the team to manually point the high-gain antenna
at Earth on Sol 2. A set of commands will then be sent to the lander on
the morning of Sol 2 to update the on-board orientation estimate.
2:20-2:50 p.m.:
The first downlink session is
conducted using the low-gain antenna. This communication session includes
spacecraft health data taken at night. It also includes images acquired
following ramp deployment at the end of Sol 1. The lander will then try
a brief session with the high-gain antenna using the new pointing information
uplinked early on Sol 2. If this communications demonstration is successful,
the team will use the high-gain antenna for the second and final downlink
on Sol 2.
If not, a second low-gain antenna session will occur between
6:30 and 7:30 p.m. After the post-ramp deploy images are received on the
ground, the rover team will make an assessment to determine if the rover
can be deployed onto the surface. If conditions allow, the rover deploy
sequence will be uplinked to the spacecraft and the rover will deploy at
about 6:15 p.m. A final set of images of the rover sitting on the surface
will then be acquired and downlinked during the final transmit session.
Nominal Mission Scenario
If the mission is on the high-gain communications
scenario and the rover was deployed on Sol 1, the following is the sequence
of events for Sol 2:
2:20-2:50 p.m.:
The first downlink session on
the high-gain antenna is conducted. This communication session includes
night data and data from the alpha proton X-ray spectrometer.
Key activities on Sol 2:
Include obtaining and
partially returning a color stereo panorama image and performing an extended
rover traverse. The rover will conduct several experiments with soil mechanics
during this traverse, and may attempt a second measurement with the alpha
proton X-ray spectrometer at the end of the day. Additional transmit sessions
may occur depending on available power; nominal time for these sessions
are 8:20-9:20 p.m. and 10:30-11:20 p.m. Data expected during these sessions
include engineering telemetry, weather observations, image data from the
stereo color panorama and images acquired by the rover.
