RHESSI's Re-entry
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|title = A Glasgow geomagnetic observation of a solar flare | |title = A Glasgow geomagnetic observation of a solar flare | ||
|number = 447 | |number = 447 | ||
- | |first_author = Pascal SAINT-HILAIRE, | + | |first_author = Pascal SAINT-HILAIRE, Albert SHIH, and Hugh HUDSON |
- | + | ||
|publish_date = April 17, 2023 | |publish_date = April 17, 2023 | ||
|next_nugget = | |next_nugget = | ||
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Our inspiration for these Nuggets, the | Our inspiration for these Nuggets, the | ||
[https://en.wikipedia.org/wiki/Reuven_Ramaty_High_Energy_Solar_Spectroscopic_Imager RHESSI] | [https://en.wikipedia.org/wiki/Reuven_Ramaty_High_Energy_Solar_Spectroscopic_Imager RHESSI] | ||
+ | hard X-ray and γ-ray observatory. | ||
went into orbit February 5, 2002, and observed the Sun successfully for | went into orbit February 5, 2002, and observed the Sun successfully for | ||
many years. | many years. | ||
- | + | Many earlier Nuggets describe its achievements, and in fact data analyses continue to the present | |
+ | (for example, the recent [https://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/Particle_Acceleration_in_Two_Coronal_Jets Nugget No. 445]) | ||
+ | Such a re-entry is the final fate of any spacecraft in | ||
[https://en.wikipedia.org/wiki/Low_Earth_orbit low Earth orbit] | [https://en.wikipedia.org/wiki/Low_Earth_orbit low Earth orbit] | ||
- | + | and the delicate and precise machinery of RHESSI will become a colorful fireball in its last moments. | |
+ | We present our own calculations of the re-entry time here, but note that | ||
+ | [https://aerospace.org/reentries Aerospace], | ||
+ | [https://www.satview.org/?sat_id=27370U SATVIEW] | ||
+ | [https://www.space-track.org/#decay SPACETRACK] and others also are watching. | ||
+ | See our updating page of [http://sprg.ssl.berkeley.edu/~shilaire/rhessi/reentry/ re-entry graphics] for more details. | ||
== Orbit predictions == | == Orbit predictions == | ||
+ | |||
+ | 19-Apr 07:00 19 Apr 2023 23:00 UTC ± 3 HOURS (Aerospace) | ||
+ | 20 Apr 2023 02:39 UTC (Spacetrack) | ||
+ | 20 Apr 2023 13:29 UTC (Satview, ex USstratcom) | ||
Figure 1 shows the predicted altitude via estimates made on Friday, April 15. | Figure 1 shows the predicted altitude via estimates made on Friday, April 15. | ||
The actual re-entry forecast time for this epoch was 20 April (Thursday) 00:05 +- 30 hours, | The actual re-entry forecast time for this epoch was 20 April (Thursday) 00:05 +- 30 hours, | ||
- | but this number will improve as we get closer to the end. | + | but this number will improve as we get closer to the end (see above). |
The final stages of re-entry are uncertain in detail because of unpredictable | The final stages of re-entry are uncertain in detail because of unpredictable | ||
fluctuations in the drag force from Earth's upper atmosphere. | fluctuations in the drag force from Earth's upper atmosphere. | ||
- | [[File: | + | [[File:447f2.png|500px|thumb|center|<b>Figure 1:</b> <i> |
- | Upper, a map of satellite tracks | + | Upper, a map of satellite tracks for the whole Earth, in a Mercator projection. |
Lower, color-coded time-series plot showing the predicted orbital altitudes. | Lower, color-coded time-series plot showing the predicted orbital altitudes. | ||
</i> | </i> | ||
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in Berkeley, California. | in Berkeley, California. | ||
- | [[File: | + | [[File:447f1.png|500px|thumb|center|<b>Figure 2:</b> <i> |
- | + | Similar to Figure 1, except for the continental US. | |
</i> | </i> | ||
]] | ]] | ||
Line 61: | Line 72: | ||
[[File:447f3.png|700px|thumb|center|<b>Figure 3:</b> <i> | [[File:447f3.png|700px|thumb|center|<b>Figure 3:</b> <i> | ||
- | More detail in a Google Maps representation. | + | More detail for the San Francisco Bay area now, in a Google Maps representation. |
</i> | </i> | ||
]] | ]] | ||
What will the observer see? | What will the observer see? | ||
- | Most | + | Most elemental materials have distinctive |
- | [https://en.wikipedia.org/wiki/Atomic_emission_spectroscopy#Flame_emission_spectroscopy flame | + | [https://en.wikipedia.org/wiki/Atomic_emission_spectroscopy#Flame_emission_spectroscopy flame spectrum] |
- | colors, and germanium is light blue. | + | colors, and germanium's is light blue. |
- | As a speculation a lucky observer might see the last moments of the RHESSI | + | As a wild speculation, a lucky observer might see the last moments of the RHESSI detectors this way. |
- | detectors this way. | + | This is very speculative, of course, as is the further thought that the tungsten |
- | This is very speculative, of course, as is the | + | grids (green flame spectrum), being massive, dense, and highly refractory, may even survive |
- | grids (green), being massive, dense, and highly | + | re-entry! |
- | re-entry | + | Do not stand underneath.... |
+ | |||
+ | == Epilogue == | ||
+ | |||
+ | Figure 4 shows the last few orbits; the final one seems to have been the pale red one (bottom at left, | ||
+ | RHESSI moving to the E). | ||
+ | According to [https://www.nasa.gov/feature/nasa-retired-solar-energy-imager-spacecraft-reenters-atmosphere definitive] | ||
+ | reporting, the end came near the Egypt/Sudan/Chad/Libya frontier area at 00:21 UT, 20 April 2023. | ||
+ | There may be some singed and interestingly slotted | ||
+ | [https://hesperia.gsfc.nasa.gov/rhessi3/mission/mission-concept/imaging/grid-pairs/index.html tungsten disks] | ||
+ | waiting to be discovered somewhere out there in the | ||
+ | [https://www.iaea.org/newscenter/news/chad-egypt-libya-and-sudan-agree-on-framework-for-joint-management-of-the-nubian-sandstone-aquifer-system Sahara desert]. | ||
+ | |||
+ | [[File:447f4.png|700px|thumb|center|<b>Figure 3:</b> <i> | ||
+ | The last moments, perhaps not too far from [https://en.wikipedia.org/wiki/Pitcairn_Islands Pitcairn Island]? | ||
+ | </i> | ||
+ | ]] | ||
+ | |||
+ | Goodbye, dear RHESSI. You are gone but these Nuggets will continue as long as your data yield interesting discoveries. |
Latest revision as of 11:07, 21 April 2023
Nugget | |
---|---|
Number: | 447 |
1st Author: | Pascal SAINT-HILAIRE, Albert SHIH, and Hugh HUDSON |
2nd Author: | |
Published: | April 17, 2023 |
Next Nugget: | |
Previous Nugget: | A Glasgow geomagnetic observation of a solar flare |
List all |
Contents |
Introduction
Our inspiration for these Nuggets, the RHESSI hard X-ray and γ-ray observatory. went into orbit February 5, 2002, and observed the Sun successfully for many years. Many earlier Nuggets describe its achievements, and in fact data analyses continue to the present (for example, the recent Nugget No. 445) Such a re-entry is the final fate of any spacecraft in low Earth orbit and the delicate and precise machinery of RHESSI will become a colorful fireball in its last moments. We present our own calculations of the re-entry time here, but note that Aerospace, SATVIEW SPACETRACK and others also are watching. See our updating page of re-entry graphics for more details.
Orbit predictions
19-Apr 07:00 19 Apr 2023 23:00 UTC ± 3 HOURS (Aerospace) 20 Apr 2023 02:39 UTC (Spacetrack) 20 Apr 2023 13:29 UTC (Satview, ex USstratcom)
Figure 1 shows the predicted altitude via estimates made on Friday, April 15. The actual re-entry forecast time for this epoch was 20 April (Thursday) 00:05 +- 30 hours, but this number will improve as we get closer to the end (see above). The final stages of re-entry are uncertain in detail because of unpredictable fluctuations in the drag force from Earth's upper atmosphere.
Observability
The re-entry will suddenly interrupt RHESSI's final orbit. The imprecision of the exact time means that it could happen anywhere along the predicted orbital path, and the conservation of momentum means that the resulting fireball will trace out that path. Figure 2 shows some of the orbits, spaced approximately at 90-minute intervals and therefore about 23-degree spacings in longitude as the Earth rotates. One can see the that RHESSI's orbit was inclined to match the latitude of its ground station (at the [Space Sciences Lab] in Berkeley, California.
As with any re-entry, we expect that visual observations of the fireball will be possible for a very lucky observer. Ideally one would have clear skies, a dark night, and the great luck of having the just the right moment along the orbital track. Figure 3 shows the local area around Berkeley, where some RHESSI-lovers may be watching.
What will the observer see? Most elemental materials have distinctive flame spectrum colors, and germanium's is light blue. As a wild speculation, a lucky observer might see the last moments of the RHESSI detectors this way. This is very speculative, of course, as is the further thought that the tungsten grids (green flame spectrum), being massive, dense, and highly refractory, may even survive re-entry! Do not stand underneath....
Epilogue
Figure 4 shows the last few orbits; the final one seems to have been the pale red one (bottom at left, RHESSI moving to the E). According to definitive reporting, the end came near the Egypt/Sudan/Chad/Libya frontier area at 00:21 UT, 20 April 2023. There may be some singed and interestingly slotted tungsten disks waiting to be discovered somewhere out there in the Sahara desert.
![](/~tohban/wiki/images/thumb/6/61/447f4.png/700px-447f4.png)
Goodbye, dear RHESSI. You are gone but these Nuggets will continue as long as your data yield interesting discoveries.
RHESSI Nugget Date | 17 April 2023 + |
RHESSI Nugget First Author | Pascal SAINT-HILAIRE, Albert SHIH, and Hugh HUDSON + |
RHESSI Nugget Index | 447 + |