validation.txt ; Paul Withers, 2006.01.07 ; Center for Space Physics, Boston University ; Description of validation efforts Tolson et al (2005) Journal of Spacecraft and Rockets Figure 3 plat vs orb Starts between 60N and 70N - OK Max value just less than 90N - OK Max value around P130 - OK Ends between 20N and 30N - OK Ls vs orb Starts just below 270deg - OK Ends just above 300deg - OK LST vs orb Starts at 18 hrs - OK then decreases to min at about 17hrs, P70-80 - OK then crosses 18 hrs at P100 - OK increases thru 24 hrs around P140 - OK finally ending at 3 hrs - OK Figure 5 acc counts vs time for P076 I only have acc in ms-2 My curve is noiser on the flanks than Tolson's - WHY? main oscillations look OK, including around peak and on outbound flank asymmetric - acc is greater at +t than at -t - OK My noise level pre-pass/post-pass is much greater than Tolson's - WHY? Figure 6 acc in ms-2 vs time for P076 pre and post-pass only, not close to periapsis Select my -450s to -200s data sdev/mean about equals sqrt(25), suggesting that someone has already taken about any offset to the best of their ability mean = 5.2E-5 ms-2, sdev = 7E-4 ms-2, range is about 3E-3 ms-2 Tolson's mean is -2.5E-4 ms-2, range is about 0.3E-3 ms-2 Difference in means probably due to removal of offset WHY difference in ranges by order of magnitude? I doubt it's a labelling (cm/mm) error because Fig 5 also shows more noise in my data than Tolson's Can it be due to angular motions? I don't see how, because angular motions aren't going to cause scattered error, but systematic error Fig 10 densities vs time for P076 My data are still too noisy Structure in rho1 is noiser for me, but consistent Structure in rho7 is same, also for rho39 5+rho39-rho7 is smaller for me than Tolson 27 mm = 200 s r39 t(T)-t(me) 10 = -13 mm = -96.3 s -97.2 s 1s 20 = -10 mm = -74.1 s -69.2 s -5s 30 = -6 mm = -44.4 s -42.2 s 2s 40 = 1.5 mm = 11.1s 4.8 s 6s 30 = 8 mm = 59.3 s 58.8 s 0.5s 20 = 12 mm = 88.9 s 86.8 s 2s 10 = 16 mm = 118.5 s 119.8 s -1s r7 05 = -16 mm = -118.5s -115.2s -3s 15 = -11 mm = -81s -82.2s 1s 25 = -8 mm = -59s -56.2s -3s 35 = -3 mm = -22s -24.2s 2s 35 = 5 mm = 37s 33s 4s 25 = 10 mm = 74s 74s 0s 15 = 14 mm = 104s 106s -2s 05 = 18 mm = 133s 137s -4s Timeshift of 3s in rho7 = <20% error in rho Same for rho39 Figure 11 rho39 vs z for P076 inbound 140 km = 2E-2 3E-1 130 km = 1E0 1E0 120 km = 4.5E0 4.1E0 110 km = 1.8E1 1.7E1 outbound 150 km = 2E-1 4E-1 140 km = 6E-1 1.2E0 130 km = 2E0 3E0 120 km = 7E0 9.3E0 110 km = 2E1 2.4E1 ??? Figure 13 rho1 vs t for several orbits P155 max = 46 kg km-3, same occurs at t=0 20 kg km-3 = -130, 70s, same for both shape looks good overall P157 20 kg km-3 at -120s, 90s on Tolson I get -120s, 100s Tolson max=28 kg km-3, I get 29.4 P199 max = 55 Tolson, 56.6 me both at -48s 40 kg km-3 at -80, -30 (me) and -78, -20 (Tolson) 20 kg km-3 at -140, 50 (me) and -146, 54 (Tolson) P280 max = 52 kg km-3 me and Tolson at 27-28 s 20 kg km-3 at -170, 73 (Tolson) and -170, 75 (me) Looks like my results match Tolson's pretty well when referenced to time, less good when referenced to altitude. Thus my altitude wrt periapsis isn't too accurate. Fig 17 rho vs t and z for P159 Max rho = 68 kg km-3 at -62 s (me) 69 kg km-3 at -64s (Tolson) 40 kg km-3 at -100s, 0s (Tolson) and -95, 0s (me) 20 kg km-3 at 120-140s, 55s (Tolson) and 120-140s, 60-70s (me) wrt t, inbound matches very well, outbound a bit worse rho at 120 km = 4E0 (out) and 7E0 (in) Tolson 4E0 (out) and 9E0 (in) (me) rho at 110 km = 1E1 (out) and 2.e3E1 (in) Tolson 1E1 (out) and 2.7E1 (in) (me) wrt z, outbound matches perfectly and inbound poorly More evidence that altitude is flawed SOLUTION ODY has two types of data: hi-rate and not. Hi-rate = sample instrument at 200 Hz, return average of every block of 200 points every 1 second What I've got from pXXXacc.dat =? Possibly the first measurement within each block of 200, say Michael Theriot's Level0_PhaseA.xls says that pXXXacc.dat is not high rate data and pXXXacc.dat is not as good as high rate data. Takashima and Wilmoth (2002) AIAA paper Figure 9 rho vs t - which rho? looks most like my rho7. T+W max rho = 38.77 at -14.44 says text, figure disagrees Figure has smaller max rho, just less than 38.0 30 kg km-3 = -53, 21 20 kg km-3 = -88, 74 10 kg km-3 = 95 inbound value is hard to pick, but looks about same Me max rho = 39 kg km-3 at t=-12s 30 = -46, 21 20 = -87, 76 10 = 100 ODYA_0001 data tables rho 110/120 in/out Comparison is not good. Difference in all cases is tens of percent But always zero when relevant lat is at north pole 120 km differences are about 2x 110 km differences Change in difference per orbit is greater late in mission than early, monotonic Comparison to Tolson rho/t plots was much better Assuming my z/t is perfect, I need to shift rho in time by 20s to get P250, P280 densities to shift by 50% This is unrealistic. Therefore rho(t) is pretty good, but rho(z) is bad, so z(t) is bad. Can martian areoid take the blame? H is about 7-8 km, say. Need to move ln(2)xH or 5 km to get 50% errors This is feasible. A (4,4) areoid acquired long ago from Tolson has about 20km difference in r(pot=pot0) from equator to pole. Shallow at pole and eq, steep at mid lats. 5 km difference in 15deg of lat is feasible This explains why match is good at pole (flat areoid) and also hints of turnover in 120in plot, which gets closest to the equator. Scale heights agree tolerably. Typical values are consistent, as are trends with orbit number. I haven't done a detailed comparison, because that would be very dependent on the fitting procedure and altitude reference. AAG QLR data Compare periapsis density only Match is excellent Examine prho/rhoX-1, where X=1,7,39 Look at mean and sdev rho1: 2.5% mean, 13% sdev rho7: 2.4%, 8.5% rho39: 1.4%, 4.6% Thus periapsis densities are very accurate No reason for densities away from periapsis to be LOTS worse, so more evidence for areoid affecting rho110 comparison AAG QL plots Compare rho(t) to plots generated by AAG during aerobraking. Select a few orbits P050 Me rhomax = 43.0 at 28s 30 kg km-3 = -21, 72s 20 = -48, 90 10 = -77, 114 AAG rhomax = 43 at 29s 30 = -25, 68 20 = -51, 91 10 = -80, 118 P150 Me rhomax = 28.7 at -52.5s 25 = -77.5, -29.5 20 = -101.5, 6.5 15 = -121.5, 67.5 10 = -136.5, 124.5 5 = -153.5, 173.5 AAG rhomax = 27.7 at -53s 25 = -67, -33 20 = -100, 0 15 = -121, 75 10 = -138, 126 5 = -155, 172 P250 Me rhomax = 62 at -83s 50 = -105, 26 40 = -116, 50 30 = -170, 67 20 = -193, 114 10 = -228, 158 AAG rhomax = 61 at -80s 50 = -105, 29 40 = -117, 50 30 = -172, 46 20 = -188, 109 10 = -226, 160