Today's launch of Arianespace Vega rocket deploying Sentinel 2A Earth observation satellite for ESA & European Commission went ahead as planned, lifting off on June 23, 2015 at exactly 01:51:58 UTC from Kourou, French Guiana. Here's a video of it, in case you missed it.

That they proceeded with the launch is however somewhat surprising to me, considering that the launch time coincided with a brewing geomagnetic storm that reached category G4 (severe) just hours before, hasn't entirely subsided by launch time, and next predicted index for hours ahead was G3 (strong):

Space Weather Overview

According to NOAA's Space Weather Prediction Center, where I acquired the top graphs from, these are descriptions for the 24-Hour Observed Maximums for radio blackouts, solar storm and geomagnetic storm indexes:

G4 (Severe) Geomagnetic Storm Impacts

  • Power systems: Possible widespread voltage control problems and some protective systems will mistakenly trip out key assets from the grid.
  • Spacecraft operations: May experience surface charging and tracking problems, corrections may be needed for orientation problems.
  • Other systems: Induced pipeline currents affect preventive measures, HF radio propagation sporadic, satellite navigation degraded for hours, low-frequency radio navigation disrupted, and aurora has been seen as low as Alabama and northern California (typically 45° geomagnetic lat.).

S3 (Strong) Solar Radiation Storm Impacts

  • Biological: Radiation hazard avoidance recommended for astronauts on EVA; passengers and crew in high-flying aircraft at high latitudes may be exposed to radiation risk.
  • Satellite operations: Single-event upsets, noise in imaging systems, and slight reduction of efficiency in solar panel are likely.
  • Other systems: Degraded HF radio propagation through the polar regions and navigation position errors likely.

R2 (Moderate) Radio Blackout Impacts

  • HF Radio: Limited blackout of HF radio communication on sunlit side, loss of radio contact for tens of minutes.
  • Navigation: Degradation of low-frequency navigation signals for tens of minutes.

And here's a few more plots from that same source for the relevant date and time (descriptions at the source, click for higher resolution images):

3-Day Satellite Environment D Region Absorption Prediction ACE Mag and SWEPAM USAF Wing KP Prediction Activity Index

Next predicted geomagnetic storm index for hours following the launch and satellites injection into Sun-synchronous orbit (SSO) was G3, then upgraded again to G4 (actual):

G3 (Strong) Geomagnetic Storm Impacts

  • Power systems: Voltage corrections may be required, false alarms triggered on some protection devices.
  • Spacecraft operations: Surface charging may occur on satellite components, drag may increase on low-Earth-orbit satellites, and corrections may be needed for orientation problems.
  • Other systems: Intermittent satellite navigation and low-frequency radio navigation problems may occur, HF radio may be intermittent, and aurora has been seen as low as Illinois and Oregon (typically 50° geomagnetic lat.).

That's quite a few scary descriptions there. So to my question;

How real are all these possible effects listed on NOAA page when it comes to final preparations for a launch and launch into a near-polar SSO while the geomagnetic and solar radiation storms last?

Specifically, is there something in particular about the Vega launch vehicle and its today's payload (Sentinel-2A) that Arianespace has decided to completely ignore space weather and proceed with the launch? I know that some past launches of smaller launch vehicles, like e.g. Antares, have been delayed because of space weather, even just threatening sunspots moving at close to solar equator just in front of Earth's orbit:

enter image description here

And these were described by some as Holy mother of all sunspots, Batman, those are HUGE! Well, today the Sun actually doesn't look much better. HMI Intensitygram from SDO/AIA:

              HMI Intensitygram

And I do apologize for a media heavy question, but I think these images tell the story. If these sunspots aren't the Holy Batman, they're at the very least the Holy Robin class, I'd say.

So, what is different between Vega and other launch vehicles whose launches were scrubbed and delayed due to space weather or even just for the threat of it? Surely it cannot be that Vega launched from near equatorial latitudes and those that were scrubbed for space weather launched from US? Because Vega still passed polar regions with its upper stage as it deployed Sentinel 2A into a near-polar (retrograde inclination of 98.5°) Sun-synchronous orbit, which then passes over any of the two polar regions about every 50 minutes in its 786 km altitude, 100.6 minute orbit.


2 Answers 2


It isn't that risky, if the proper precautions are taken. The key item, as it is in most cases with spaceflight, is redundancy. There is a larger chance of single event upsets during a geomagnetic storm. This can be mitigated by hardware redundancies.

In addition, geomagnetic storms only really become an issue for most spacecraft when they are beyond LEO. As most rockets don't fire beyond LEO, it isn't much of a concern.

Some rocket companies choose to not invest as much in testing and redundancy, and thus when a geomagnetic storm happens, there is more to be concerned with. Antares was one you specifically mentioned. The COTS (Commercial Orbital Transportation Services) ISS payload system has been considered relatively low priority, thus, if the mission has to be delayed a day to ensure no issues, it is of little impact. More commonly used rockets need to have higher safeguards, which not only protect against solar storms, but also will give the rocket an overall higher reliability, thus they are more protected.

If you think about it, many satellites operate through solar storms all the time, thus, it can easily be done, if you invest the time and money to get it right ahead of time.


Somewhat risky: SpaceX announced on 2022-02-08 that they lost 40 Starlink satellites because a geomagnetic storm increased drag at the orbit altitude (just 210 km just after launch) so much that the satellites deorbited:

On Thursday, February 3 at 1:13 p.m. EST, Falcon 9 launched 49 Starlink satellites to low Earth orbit from Launch Complex 39A (LC-39A) at Kennedy Space Center in Florida. Falcon 9’s second stage deployed the satellites into their intended orbit, with a perigee of approximately 210 kilometers above Earth, and each satellite achieved controlled flight. [...]
Unfortunately, the satellites deployed on Thursday were significantly impacted by a geomagnetic storm on Friday. These storms cause the atmosphere to warm and atmospheric density at our low deployment altitudes to increase. In fact, onboard GPS suggests the escalation speed and severity of the storm caused atmospheric drag to increase up to 50 percent higher than during previous launches. [...]
Preliminary analysis show the increased drag at the low altitudes prevented the satellites from leaving safe-mode to begin orbit raising maneuvers, and up to 40 of the satellites will reenter or already have reentered the Earth’s atmosphere.

  • $\begingroup$ Up to 80% failure from one launch, ouch! $\endgroup$ Feb 9, 2022 at 17:41
  • $\begingroup$ From the article... atmospheric drag increased "up to 50%" higher!!! $\endgroup$
    – Dagelf
    Feb 9, 2022 at 19:27
  • $\begingroup$ @BrendanLuke15 loss, not failure...the satellites are/were still functional (as far as anyone knows), just stuck in safe mode in a low orbit where the puffed-up atmosphere gave them a very short orbital lifetime. $\endgroup$ Feb 10, 2022 at 1:10
  • $\begingroup$ @ChristopherJamesHuff six of one, half a dozen of the other $\endgroup$ Feb 10, 2022 at 1:16

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