Dr. Sten Odenwald
NASA/HEAT
Artistic rendering of the Parker encounter. (Credit: ASA/Johns Hopkins APL/Steve Gribben)
Here is a handy table that summarizes the circumstances for the Parker Solar Probe perihelia since 2018. Nothing fancy – just a one-stop-shop for those of you who want a convenient summary of all of the encounters, rather than having to scour the internet to find them.
Surface = center – 0.6957
Methodology.
For those of you who are interested in how I put this table together, here are the 14 steps I used.
1) Found perihelion dates from the PSP Timeline at
https://www.parkersolarprobe.jhuapl.edu/The-Mission/index.php#Timeline
2) Entered the perihelion date into the Spacecraft Tracker
https://psp-gateway.jhuapl.edu/website/Tools/SpacecraftTracker
3) At bottom of the web page, selected ‘Get Data (csv)’ and saved the .csv file as OrbitN.xls Excel Workbook file. The columns give: A) UT date and time; B-D the x,y,z coordinates of the spacecraft in kilometers.
4) Computed the distance to the sun’s center using R = (x2+y2+z2)1/2 in 5th column.
5) Plotted R
6) Found date, time and R for the minimum distance shown with the star in the above plot.
7) Found the indicated sample number (712) in the file
8) Entered this information in the above perihelia table.
9) Returned to the PSP portal page at
https://psp-gateway.jhuapl.edu/
10) At the bottom of the page, selected ‘Instrument Data Plots’. Data is not yet available for dates after June 2024, so the next example is for March 30, 2024 Orbit 19. Enter this date in the input bar. The following plot will appear. Data on the ambient density will be in the top plot. If it is missing, click on the ‘Next’ or ‘Previous’ bar to call up the next data in the time series.
11) Clicking on ‘Next’ brought the following data panel
12) This shows the proton density in the top panel. The valid data starts at the far-right. The data is in logarithmic units. The data appears between Log(100) = 2.0 and Log(1000) = 3.0 ,so estimate that it is at Log (D) = 2.5 so that the density D = 316 protons/cm3. Enter this number rounded to 300 in the above table for Orbit 19. The actual date for the measurement is indicated in the parenthesis. The most reliable densities occur for measurements made close to the date of the perihelion, example, Orbits 1, 2 and 4.
13) The ambient spacecraft temperature on the heat shield is calculated from the formula
Where L is the solar luminosity 3.86×1026 Watts, R is the distance to the sun in meters, and ‘sigma’ is the Stefan-Boltzmann Constant 5.67 x 10-8. Solving for the temperature and evaluating the constants we get
14) For Orbit 22 at a distance of R = 6.863 million km, we get T = 1841 kelvins or T = 1841.8-273.15 = 1569o Celsius, which is entered in the table column 6.