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Phoenix

Phoenix. The Phoenix mission was the first mission in NASA’s Scout Program . Phoenix launched on a Delta II 7925 rocket from Cape Canaveral Air Force Station on 4 August 2007.

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Phoenix

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  1. Phoenix • The Phoenix mission was the first mission in NASA’s Scout Program. • Phoenix launched on a Delta II 7925 rocket from Cape Canaveral Air Force Station on 4 August 2007. • After a 10-month journey from Earth to Mars, Phoenix performed the first soft landing on Mars since the two Viking probes landed on Mars in 1976.

  2. Phoenix Landing Phoenix successfully landed on the northern plains of Mars on 25 May 2008 (Vastitas Borealis region at 68.219 deg North Latitude and 234.248 deg East Longitude).

  3. The Entry, Descent, and Landing (EDL) The Entry, Descent, and Landing (EDL) phase had many critical events occurring over a short period of time, including cruise stage separation, entry into the Martian atmosphere, parachute deployment, lander separation, and terminal descent. The X-band telecom subsystem was jettisoned with the cruise stage upon separation, with all subsequent EDL (and surface) communications through the UHF subsystem.

  4. EDL Communications NASA levied a requirement on the Phoenix mission to provide telecommunications coverage during all critical events, such as EDL, sufficient to diagnose faults and/or failures, should they occur The EDL comm architecture relied on establishing primary data links to relay spacecraft orbiting Mars. A UHF relay link via an orbiting asset allows for a significant increase in data rate due to its relatively close proximity to the landing spacecraft compared to a direct-to-Earth (DTE) X-band link. The latter relies on terrestrial assets only and because the distance to Earth is vastly larger than to a relay orbiter, the signal space loss is larger and, ultimately, the supportable data rate is distinctively reduced. Mars Odyssey (ODY) Mars Reconnaissance Orbiter (MRO) and Mars Express spacecraft were operational during EDL and thus supported EDL comm. Greenbank The entire Phoenix entry descent and landing (EDL) was observable by NASA mission control teams and the public in real-time, delayed only by the one-way light time, thanks to Phoenix's EDL Communications. Phoenix EDL comm successfully operated throughout the entire EDL sequence and allowed the mission control teams to observe the events as they unfolded (delayed only by the one-way light time).

  5. PHX EDL Comm - A few "firsts" 4 parallel pipelines for EDL Comm 32kbits/s - highest data rate so far (see table below) Customized slewing profiles to minimize antenna off-boresight angles Open-loop recording and subsequent TLM extraction International participation (ESA's Mars Express)

  6. Top-Level EDL Comm Data Flow

  7. EDL Comm Event Visibility

  8. All three orbiters sampled and recorded the incoming signal using their respective canister and open-loop recording modes. Once on the ground, a Fast-Fourier-Transform (FFT) was applied to the data sets to obtain a spectrogram, i.e. a frequency vs. time plot, and an associated spectral movie. The latter corresponds to what an observer would see on an spectrum analyzer had there been one at the input to the orbiter receiver during EDL. Next, a peak search algorithm was applied to search for strongest signal in the spectrum at any given time and extract its carrier frequency and signal peak power. When performed over the entire EDL duration, a Doppler and relative peak power profile of the UHF signals recorded by the orbiters' transceivers could be established. The latter peak search algorithm was used in real-time to process and display the UHF signal recorded by ODY as well as post-process the MRO and MEX data shortly after these data sets were received.

  9. Recorded MRO Spectrum

  10. MRO Doppler - Actual vs. Predicted

  11. Direct-to-Earth transmission The Green Bank Telescope (GBT) was used to receive the UHF as a direct to Earth (DTE) transmission during EDL. The RSR used an a-priori prediction file of the Doppler profile based on navigation information and recorded any deviations from it during EDL. The latter, also referred to as residual frequency, when added to a-priori Doppler profile yields the actual Doppler profile encountered during EDL. Because residual frequency is the difference between the expected and actual Doppler profiles, it sweeps a smaller frequency range and allows for easier determination of signal presence.

  12. DTE RSR Residual Frequency

  13. DTE RSR Doppler

  14. Low Altitude Winds Latitude Longitude

  15. Winds from LMD Climate Data Base

  16. Summary • Phoenix descent profile Doppler observation can potentially contribute to wind speed measurements, data that are lacking from current input to GCM • We processed (preliminarily) the Direct-to-Earth UHF data captured at GBT which give one vector direction (LOS) • Will process relay Doppler to MRO, ODY, and MEX to reconstruct 3-D… • Range of measurements observed 2 to 20 m/s • Consistent with GCM models for Ls, location, etc.

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