MARS CORRECT BASIC REPORT - SECTIONS 10

HOME PAGE Web Site Contents Mars Report Contents Mars Report Abstract CV for Dr. David Roffman Diplomas PhD Thesis PhD Thesis Powerpoint Mars PowerPoint MSL Weather Reports Seasonal Pressure Altitude Calculations MSL Year 4 Spring Weather MSL Yr 3-4 Winter Weather MSL Fall Yr 3 Weather MSL Yr. 3 Summer Weather MSL Yr. 3 Spring Weather Martian plume March 25 2017 MSL Ultraviolet 3 YEARS OF MSL UV Desai, EDL, Parachutes & ExoMars Mars winter vs. summer temps Helo to Mars Sea at Utopia Planitia, Mars Tree Stump at MSL? Spherical life on Mars? Mars Report Abstract, 1-1.2 Mars Report Sec.2-2.1 Report 2.2-2.4 Report 2.5-2.5.2 Report 2.5.3-2.7 Report 3-4 Report 4.1-4.1.2 Report 5 to 6 Report  7-7.2.1 Report 8 Report 9 Report 10 Report 11 Global Dust Storm Report 12 Report  13-13.2 Report 13.3-13.5 Report 13.6 Report 14-15 Report 15.1 Report 15.2-15.3 Report 15.4-15.6.2 Report 15.6.2.1 - 15.6.2.3 Report 15.6.2.4-15.7 Report 16-16.1 Report 17-20 Report References Report Afterword Rebuttal of REMS Report Running water on Mars MSL Year 0 Weather MSL Yr 2 Winter-Spring Weather MSL Yr 2 Summer Weather MSL Yr 2 Fall Weather MSL Yr 2-3 Winter Weather Adiabatics MSL Hi Temps MSL Low Temps Organic Chem found by MSL Oxygen in Mars Air MSL Day length & Temp Warm winter ground temps 155-Mile High Mars Plume Radiation Diurnal Air Temp Variation Mars Temps Fahrenheit Beagle found JPL/NASA Pressure Mistakes Enter MarsCorrect Sol 370, 1160 & 1161 Histories Mars-Radio-Show JPL Fudges Pressure Curves MSL Temp. ∆ Mast to Ground High & Low Pressures Normalized Mars soil 2% water Moving rock Mars MAVEN MSL Relative Humidity Claim Ashima Concedes Original MSL Weather Record Old MSL Weather Record MSL Summer Weather Pressure Estimate REMS Wind MSL Pressures REMS Reports Curiosity Geology CERN-2013-pics Daylight Math MSL Errors P1 MSL Errors P2 MSL-Chute-Flap MSL daylight Ashima Sols 15 to 111 Ashima Sol 112 to 226 Ashima Sol 227 on New Ashima Sols 270+ MSL Summer to Sol 316 Updated Secrets of Mars Weather Forecast Wind Booms MSL Credibility MSL Temp. Swings MSL Temperatures Sample Analysis at Mars (SAM) VL2 - MSL Ls Comparson Ashima MIT Mars GCM Dust Storm Nonsense Mars Slideshow Moving Sand & Martian Wind 3 DEC12 Press Conf. MSL Press Conf. 15NOV2012 Sol Numbering MSL Pressure Graph to Ls 218.8 MSL Sky Color Mars Sky Color DATA DEBATE! Zubrin's Letter Phoenix Vaisala Vaisala Pressure Sensors Phoenix &MSL Flawed MSL REMS Viking pressure sensors failed MSL landing site Mars Landings Phobos Grunt Martian Air Supersaturation Mars & CH4 Mars and MSL Time Viking Pressure Audit Links Mars Society 2008 Quant Finance Frontiers Home Front. Preface Frontiers Ch. 1 Frontiers Ch. 2 Antimatter Lightning Frontiers Ch. 3 Frontiers Ch. 4 Frontiers Ch. 5 Frontiers Ch. 6 Frontiers Ch. 7 Frontiers Ch. 8 Frontiers Ch. 9 Frontiers Ch 10 Frontiers Ch 11 Frontiers Ch 12 Frontiers Ch 13 Frontiers Ch 14 Frontiers Ch 15 Frontiers Ch 16 Frontiers Ch 17 Frontiers Ch 18 Frontiers Ch 19 Frontiers Ch 20 Frontiers Ch 21 Frontiers Ch 22 World Tour Spring-Break -13 Other Travels Asteroid Impact? ExoMars data Unit Issues Viking Pressures Tavis CADs Landing Long Scale Heights LS of Max/Min Pressures Tavis Report Tavis Failures Lander Altitude Martian Trees? Code Experiment Gedanken Report Mars Nuke? Martian Flares Mach Numbers MOLA (altitude) Original Mars Report Mariner 9 & Pressure Mars  Temps MSL Time MPF Pressure Blog Debates Spring Pendulum Plasma Model Reporting Errors Orbital Parameters Anderson Localization P. 1 Anderson Localization P. 2 Moving rock old Navigating Mars Mars Report Section Links Mars Report Figure Link Gillespie Lake rock outcrop MSL Sol 200 Anomaly Sol 1300&1301 Anomalies Gilbert Levin & Labeled Release Brine on Mars Ceres Lights Yr 1 Table 1 Missing data Mitchell Report Old Mars Report All MPF Temps ExoMars fails Did Spirit find past life? MSL ground temps go haywire OPACITY AT MSL Luminescence on Mars Dust Storms & Microorganisms 2018 Global Dust Storm

Mars Global Surveyor Excessive Aeroraking (Updated 9/14/2018)

EXCESSIVE DECELERATION DURING AEROBRAKING OPERATIONS.      

       It is cost efficient to slow a spacecraft approaching a planet like Mars by aerobraking – dipping the probe into the atmosphere to use free drag rather than expensive fuel.  This was done with Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO).  In both cases, more air was encountered than expected.

10.1 Mars Global Surveyor (MGS).  

       When MGS was launched in 1996, the intent was to achieve a circular pole-to-pole, Sun-synchronous orbit around Mars with an altitude of approximately 300 km above the surface and an orbital period of just under 2 hours. In an attempt to accomplish this orbit using minimal fuel, MGS used aerobraking. It was deliberately flown through the upper atmosphere of Mars during periapse to use the aerodynamic drag forces to modify its orbital parameters.  The effort did not go as planned and the early maneuvers led to excessive decelerations (Read & Lewis 2004, 11).78

       If Mars has a higher than expected atmospheric density, it would explain unexpected excessive decelerations.  As shown in Figure 40 and discussion below, it is believed that a dust storm produced the unexpected drag, but the effects at a normalized altitude of 121 km (75 miles) seem quite high for a planet that is supposed to have an average surface pressure of only about 6.1 mbar.

       Johnston et al.  (1998)81 reported that (1) “On the onset of a dust storm, the atmospheric density could more than double in a 48 hour time period,” and (2) “If during aerobraking, the spacecraft experiences dynamic pressure values greater than this limit line, the periapsis altitude of the orbit must be raised immediately in order to re-establish the 90% atmospheric density capability.”  Both happened. 

       Note the tremendous increase in dynamic pressure shown on Figure 39.  At an altitude normalized to 121 km, the dust storm caused dynamic pressure to rise from about 0.15 N/m2 on November 9th, 1997 to 0.84 N/m2 on December 7, 1997. While the Johnson et al. (1998) article referred to atmospheric density more than doubling during a dust storm, the increase in dynamic pressure felt at 121 km over four weeks was 5.6 times the pre-storm values.

Figure 39 Actual Dynamic Pressure Normalized to an Altitude of 121 km (reproduced from Johnson, et al, 1998)

 

Figure 39 – Actual Dynamic Pressure – Normalized to an Altitude of 121 km (reproduced from Johnson, et al, 1998)

 

10.2 Mars Reconnaissance Orbiter (MRO).  

        MRO also employed an aerobraking process. Its navigation team relied on an atmospheric model called the Mars-GRAM (Global Reference Atmospheric Model).  Mars-GRAM is a computer database of information from what previous missions have encountered. It provided a prediction of the atmospheric density, giving the navigators an estimate of how far down into the atmosphere the spacecraft should go.

       The atmospheric density that MRO actually experienced was much different than what was predicted by the Mars GRAM (Atkinson, 2006).82 Two quotes are most notable in the Atkinson article:

(1) “At some points in the atmosphere, we saw a difference in the atmospheric density by a factor of 1.3, which means it was 30% higher than the model,” said Han You, Navigation Team Chief for MRO. “That’s quite a bit, but around the South Pole we saw an even larger scale factor of up to 4.5, so that means it was 350% off of the Mars GRAM model.”

(2) “When we first started out at a somewhat higher altitude, the Mars GRAM model was doing pretty well,” said Richard Zurek, Project Scientist for MRO. “When we got to the lower altitude the scale factor to which it was off was larger and it became even larger as periapsis moved toward the South Pole.”

.     

This report is continued with Section 11 here.