Final Cruise Events
Entry, Descent and Landing
Nominal Mission Scenario
|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.|
|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.|
|Mars Pathfinder is about 696,000 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.|
|Mars Pathfinder is about 408,000 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.|
|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.|
|Cruise stage separation.|
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:
Landing on surface of Mars in Ares Vallis. Transmitter turned off shortly after landing to save power.
After touchdown, the following sequence will occur:
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.
|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 pm||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.|
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:
|Date||Time (PDT)||Nominal Mission Event|
|The camera on the lander is released and begins searching for the Sun. The high-gain communications antenna is deployed and pointed toward Earth.|
|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.|
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).
|Date||Time (PDT)||Low-Gain Communications Scenario Event|
|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.|
|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.|
|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.|
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 any time which may change this timeline. As always, the highest priority will be to assure the safety of the spacecraft and rover, and to ensure enough power for operations and to recharge the battery.
|Date||Time (PDT)||Nominal Mission Event|
|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.|
|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.|
|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).|
|July 4||8:58 pm||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.|
|July 4||9:24 - 10:26 pm||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.|
|July 4||10:30 pm||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.|
Resuming this scenario in the event that the high-gain antenna is not deployed on the first day:
|Date||Time (PDT)||Low-Gain Scenario Communications Event|
|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.|
|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.|
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:
|Date||Time (PDT)||Nominal Mission Event|
|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.
Back to the top of the page.
Back to the Mars Pathfinder Home Page.