Interview experience
ISRO interview experiences covering GATE score shortlisting, Personal Interview, Document verification & medical. Round-wise notes, common questions, and what candidates report clears each stage.
ISRO Interview Questions and Answers (2026)
ISRO is India's national space agency, founded in 1969 and headquartered in Bengaluru, responsible for satellite launches and space exploration missions. Fresh engineering graduates typically join as Scientist/Engineer SC through the ICRB recruitment exam, working on rockets, satellites, and deep space programs.
Explore: Interview experience · HR interview questions · Overview · Placement papers · Preparation guide
Overview
ISRO’s main fresher engineering hire - Scientist/Engineer ‘SC’ - runs mostly on your GATE score in recent cycles: GATE-based shortlisting (an ICRB written test in some cycles and disciplines) followed by a single Personal Interview.
HR interview questions
ISRO HR interview questions with sample answer frameworks - motivation, relocation, STAR stories, and culture-fit prompts.
ISRO interview process at a glance
| Round | Duration | What it tests |
|---|---|---|
| GATE score shortlisting | - | Valid GATE score in the matching engineering discipline, shortlisted 1:7 against vacancies |
| Personal Interview | 30-45 min | Technical/academic depth (40), specialisation awareness (20), communication (20), comprehension (10), academic record (10) |
| Document verification & medical | - | Eligibility documents, category certificates, physical fitness |
ISRO ICRB recruitment: quick answers
ISRO’s Scientist/Engineer ‘SC’ hiring runs through the ISRO Centralised Recruitment Board (ICRB), and the screening mode changes between cycles. These answers are compiled from summaries of the 2025 ICRB advertisement (ISRO:ICRB:01(EMC):2025) by Physics Wallah and ResultBharat, and from candidate reports; the advertisement on isro.gov.in is final.
| Question | Answer |
|---|---|
| Is GATE required? | In recent cycles for Electronics, Computer Science and Mechanical, yes: shortlisting is on a valid GATE score in the matching paper (EC, ME or CS). The 2025 cycle (applications 29 April to 19 May 2025) had 63 posts: Electronics 22, Mechanical 33, Computer Science 8. Other disciplines and earlier cycles used an ICRB written test instead. |
| What is the written test like, when there is one? | About 80 discipline MCQs in 90 minutes, with negative marking, at GATE and ESE depth. |
| Does it have negative marking? | Only in the ICRB written test or in GATE itself. The GATE route adds no ISRO test. |
| How much is the cutoff? | Not published in advance. 1:7 candidates per vacancy are called by GATE score. Physics Wallah reports 2025 shortlist cutoffs of about 721 (Electronics), 801 (Mechanical) and 813 (Computer Science) GATE score. |
| How much does the interview count? | Reports conflict. Physics Wallah’s 2025 summary says final selection is 50% GATE and 50% interview; several older candidate reports say the screening score was not added and selection rested on the interview. Read your advertisement. |
| How is the interview scored? | Older candidate reports give 100 marks: technical and academic depth 40, specialisation awareness 20, communication 20, comprehension 10, academic record 10. |
| What is the eligibility? | 65% aggregate (average of all semesters) or CGPA 6.84/10 in B.E./B.Tech. in the advertised discipline, confirmed for the 2025 cycle. Maximum age 28 as on 19 May 2025, with relaxations. Pay Level 10, basic Rs 56,100. |
| Is there coding? | No coding test. CS panels may ask you to write or derive on a whiteboard. |
ISRO interview questions by discipline
These are questions candidates have reported on GeeksforGeeks and ERForum; they show the level, not a fixed list.
| Discipline | Reported questions and topics |
|---|---|
| Electronics / ECE | Convert a sine wave to a square wave and back. Cascading band-pass filters and the resulting bandwidth, Q factor. Cutoff frequency in waveguides. Logic families by speed and power. ADC types and which is fastest. Microcontroller vs processor, RAM and ROM types. Helmholtz equation in 1-D, then 3-D. |
| VLSI (Scientist ‘C’ / M.Tech) | VLSI design flow and low-power techniques. 180 nm vs 5 nm. Op-amp feedback types and CMRR. IGBT and Schottky contacts. Amplifier classes and efficiency. Bandpass sampling and gate delay. |
| Computer Science | OS, DBMS, computer networks and security, with heavy weight on security. B.Tech project in depth. Software engineering even if you did not list it. Whiteboard derivations. |
| Mechanical | Few detailed public reports. Expect thermodynamics, strength of materials and propulsion basics tied to launch vehicles, plus your project. |
Asked across every discipline: a brief introduction, your 3 to 5 favourite subjects (then why, how and applications), your project, ISRO’s current missions and launch vehicles, and your preferred centre and willingness to relocate.
GATE score shortlisting
Recent ICRB cycles, including the 2025 one, shortlist Electronics, Computer Science and Mechanical candidates on a valid GATE score in the matching paper (1:7 against vacancies - the effective cutoff moves every year). Other disciplines and some notifications still run an ICRB-written test (typically ~80 discipline MCQs in 90–120 minutes, negative marking on technical sections in several past papers) before the interview. Always confirm the mode in the live advertisement on isro.gov.in - do not assume every cycle is GATE-only.
What to prep if a written test is listed
- Discipline MCQs at undergraduate/GATE-syllabus depth (speed matters)
- Space-technology and general-awareness items tied to ISRO programmes (candidate reports)
- No separate LeetCode-style coding section in standard Scientist/Engineer ‘SC’ write-ups
Personal Interview
A single 100-mark interview does all the technical and behavioural evaluation. Panels lean hard on your GATE-syllabus subjects and expect you to explain your final-year project clearly and in depth, since Comprehension and Presentation/Communication are scored as separate criteria alongside raw technical knowledge.
Common questions
- Core subject questions from your GATE discipline (e.g. control systems, thermodynamics, structures, VLSI, depending on branch)
- Panels often ask you to name 3–5 favourite subjects, then drill with why / how / advantages / applications follow-ups (LinkedIn selection reports)
- General-awareness questions on ISRO’s current missions (Chandrayaan-3, Aditya-L1, Gaganyaan, NAVIC) and launch vehicles (PSLV, LVM3, SSLV)
- Detailed walkthrough of your final-year project or thesis - methodology, results, and what you’d change; whiteboard derivations are common (GFG Bengaluru CS experience)
- Why ISRO, preferred centre or division, willingness to relocate
- Motivation and integrity prompts (bond, long mission timelines) - often woven into the same sitting, not a separate HR round
Sample answer frameworks for the interview are on the ISRO HR interview questions page.
Why there’s often no written exam or GD at ISRO
Unlike IOCL or NTPC, which sometimes add a Group Discussion, or apprentice-style PSU entries that run their own computer-based test, ISRO’s Scientist/Engineer ‘SC’ recruitment (via ICRB) has stripped the pipeline down to GATE score plus interview. That means your prep timeline is compressed into two things: getting a competitive GATE score in your discipline, and then treating the single interview as the only scored round after shortlisting (half of final merit in the 2025 cycle, per Physics Wallah) - there’s no second technical round to recover a weak interview performance.
ISRO ICRB vs centre-level recruitment
ICRB is ISRO’s central board for Scientist/Engineer ‘SC’ posts across centres, and it is what this page covers: one advertisement, GATE or written screening, a single interview and posting to any ISRO centre.
Individual centres such as VSSC, URSC, SAC and SDSC SHAR also advertise their own posts, mostly Technical Assistant, Scientific Assistant, Technician and some centre-specific Scientist/Engineer roles. These are separate advertisements with their own written and skill tests, eligibility and posting at that centre. If the advertisement is issued by a centre rather than by ICRB, prepare for its own test pattern rather than the GATE route described here.
Common technical interview questions and answers
Q: What does negative feedback do to a control system, and how do you check stability?
Negative feedback subtracts a measured output from the reference input, so the controller acts on the error. That reduces sensitivity to plant parameter variation and disturbances, widens bandwidth and improves linearity, at the cost of reduced overall gain and a risk of instability if the loop phase shift approaches 180 degrees while the loop gain is still above unity. For a linear time-invariant system, stability means every closed-loop pole lies in the left half of the s-plane. You test this without factoring the characteristic polynomial using the Routh-Hurwitz criterion - the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles - or graphically with gain and phase margins on a Bode plot.
Q: State the sampling theorem and explain aliasing.
The Nyquist-Shannon sampling theorem says a signal band-limited to a maximum frequency fm can be reconstructed exactly from samples taken at a rate greater than 2fm; that threshold, 2fm, is the Nyquist rate. If you sample slower, frequency components above half the sampling rate fold back and appear as lower frequencies that are indistinguishable from genuine ones - that is aliasing, and no processing afterwards can undo it. The fix is an analogue anti-aliasing low-pass filter before the ADC, which is why every real telemetry or imaging chain places the filter ahead of the sampler rather than after it.
Q: What are setup time and hold time in a digital circuit?
Setup time is the interval before the active clock edge during which the data input must already be stable; hold time is the interval after the edge during which it must stay stable. Violate either and the flip-flop can go metastable, settling to an unpredictable value after an unbounded delay. A setup violation means the data path is too slow, so you fix it by shortening combinational logic, pipelining, or lowering the clock frequency. A hold violation means the path is too fast and is independent of clock period, so you fix it by adding buffer delay in the data path. Crossing clock domains needs a synchroniser, typically two cascaded flip-flops.
Q: State the first and second laws of thermodynamics and explain Carnot efficiency.
The first law is conservation of energy for a system: the heat added equals the change in internal energy plus the work done, or dQ = dU + dW. It says energy cannot be created or destroyed but places no limit on direction. The second law supplies that direction - entropy of an isolated system never decreases, and no engine can convert heat entirely into work while operating in a cycle. The Carnot cycle sets the upper bound on efficiency between two reservoirs: efficiency = 1 minus T_cold divided by T_hot, with temperatures in kelvin. So an engine between 800 K and 300 K cannot exceed 62.5 percent, no matter how it is built - a real engine is always lower because of irreversibilities.
Q: What is the difference between stress and strain, and what does the stress-strain curve tell you?
Stress is internal force per unit area (N/m squared, or pascal); strain is the resulting fractional deformation, change in length over original length, and is dimensionless. In the initial linear region they follow Hooke’s law, stress = E times strain, where E is Young’s modulus - the slope, a measure of stiffness. The curve then passes the proportional limit and yield point, after which deformation is plastic and permanent, rises to the ultimate tensile strength, and ends at fracture. A ductile material like mild steel shows a long plastic region and necking before failure, while a brittle material like cast iron fractures with almost no plastic warning - which is why launch-vehicle structures are designed with yield and ultimate factors of safety against limit loads.
Q: What is the rocket equation, and what does specific impulse mean?
Tsiolkovsky’s rocket equation gives the velocity change a rocket stage can produce: delta-v = Ve times the natural log of initial mass divided by final mass, where Ve is the effective exhaust velocity. Because the mass ratio sits inside a logarithm, propellant requirement grows exponentially with the required delta-v - the reason launch vehicles like PSLV and LVM3 are staged, dropping empty tanks to keep the mass ratio favourable. Specific impulse, Isp, is thrust per unit weight flow rate of propellant, measured in seconds, and relates to exhaust velocity as Ve = Isp times g0. Solid boosters sit near 250-290 s, storable liquids near 300 s, and cryogenic LOX-LH2 engines near 440 s in vacuum, which is why cryogenic upper stages matter for heavy GTO missions.
Q: Why is a geostationary orbit at about 36,000 km, and how does a sun-synchronous orbit differ?
A geostationary satellite must complete one orbit in exactly one sidereal day (23 h 56 m) so it appears fixed over a point on the equator. Equating gravitational and centripetal acceleration gives an orbital radius of about 42,164 km from Earth’s centre, which is roughly 35,786 km of altitude, and the orbit must be equatorial with near-zero inclination - that is where communication satellites such as the GSAT series sit. A sun-synchronous orbit is a low, near-polar orbit at roughly 600 to 900 km with an inclination near 98 degrees, slightly retrograde. Earth’s equatorial bulge (the J2 term) precesses its orbital plane by about one degree per day, matching Earth’s motion around the Sun, so the satellite crosses every latitude at the same local solar time - giving the consistent lighting that remote-sensing missions like Cartosat and Resourcesat need.
Q: What is escape velocity, and how does it relate to orbital velocity?
Escape velocity is the speed at which an object’s kinetic energy equals the magnitude of its gravitational potential energy, so it can leave a body’s gravitational influence with zero residual speed: Ve = square root of 2GM divided by r, which is about 11.2 km/s at Earth’s surface. Orbital velocity for a circular orbit is Vo = square root of GM divided by r, about 7.9 km/s near the surface and around 7.8 km/s in low Earth orbit. So escape velocity is exactly root-two times circular orbital velocity at the same radius - roughly 41 percent more speed. Note it is a speed, not a direction, and it ignores atmospheric drag, which is why real launch profiles pitch over and gain altitude before accelerating hard.
Q: What is a satellite link budget, and why does ISRO care?
A link budget accounts for transmit power, antenna gains, path loss (free-space loss plus atmospheric and rain fade), and receiver noise to estimate received SNR or Eb/N0. If the budget closes with margin, the ground station can demodulate telemetry reliably; if not, you add power, bigger dishes, better channel coding, or lower data rate. Spacecraft panels care because every watt and every decibel is mass, thermal, and power-subsystem cost - this is applied communications engineering, not memorising a formula sheet.
Q: How do PSLV and GSLV (LVM3) differ in mission role?
PSLV is the workhorse for Sun-synchronous and many LEO science/Earth-observation missions, using a four-stage solid/liquid stack. LVM3 (GSLV Mk III) is the heavy-lift path for higher-mass GTO inserts and flagship missions that need more throw mass. The interview angle is matching vehicle capability to orbit and payload mass, not ranking one rocket as universally “better.”
Q: What is NAVIC, and how is it different from GPS?
NAVIC (IRNSS) is India’s regional navigation system - seven satellites in geosynchronous and inclined geosynchronous orbits giving primary service over India and surrounding regions. GPS is a US global constellation. Both use ranging from multiple satellites; NAVIC improves availability over the Indian landmass. Be ready to explain why a country invests in regional navigation (autonomy, restricted services, augmentation) without claiming GPS is “worse.”
Q: Explain virtual memory and why an OS uses it.
Virtual memory maps each process’s virtual pages to physical frames via page tables and the MMU; a page fault triggers a load from backing store or frame allocation. It gives isolation, lets the sum of process spaces exceed RAM, and simplifies loading. Trade-offs include TLB pressure, fault latency, and thrashing when the working set does not fit - common OS ground when CS panels connect flight software to platform fundamentals.
Frequently asked questions about ISRO interviews
Is there negative marking in ISRO Scientist/Engineer recruitment?
Not on the GATE route - ISRO adds no test of its own, so the only negative marking is GATE’s. Cycles that used an ICRB written test (about 80 discipline MCQs in 90 minutes) did have negative marking, so check which mode your advertisement uses.
What is the ISRO Scientist/Engineer SC cutoff?
ISRO does not publish a GATE cutoff in advance; it shortlists 7 candidates per vacancy in each discipline by GATE score, so the line moves every year. Physics Wallah reports the 2025 shortlist (Advt. ISRO:ICRB:01(EMC):2025) closed at GATE scores of about 721 for Electronics, 801 for Mechanical and 813 for Computer Science. In older written-test cycles one ECE candidate’s guide aimed to attempt 50+ of 80 questions and score above 120.
What is the ISRO interview process for freshers?
ISRO hires Scientist/Engineer ‘SC’ - its main fresher engineering entry - through the ISRO Centralised Recruitment Board (ICRB) using a GATE-score route: 1. Candidates are shortlisted purely on their valid GATE score in the matching discipline, at 1:7 against vacancies - there is no separate ISRO written exam on this route (some earlier cycles used an ICRB written test instead). 2. A single Personal Interview (older candidate reports give 100 marks: Technical/Academic Knowledge 40, General Awareness in your specialisation 20, Presentation and Communication 20, Comprehension 10, Academic Achievements 10). Physics Wallah’s summary of the 2025 advertisement says final selection combines GATE and interview at 50:50. 3. Document verification and medical examination. The full cycle from GATE score release to offer typically runs a few months.
Is there a written test for ISRO recruitment, or is it only GATE-based?
It depends on the cycle: recent ICRB cycles for Electronics, Computer Science and Mechanical - most recently ISRO:ICRB:01(EMC):2025, 63 posts - shortlisted on GATE score with no ISRO written exam, while earlier cycles and some disciplines used an ICRB written test (about 80 MCQs in 90 minutes) before the interview. ISRO also occasionally runs direct recruitment drives (e.g. for Technical Assistant or other non-GATE posts) that do use their own written/computer-based test, but for degree-engineer hiring the GATE route is the dominant path today.
What questions are asked in the ISRO interview?
The ISRO Personal Interview is discipline-heavy: expect deep technical/academic questions from your core engineering subjects (as covered in your GATE syllabus), general-awareness questions tied to your specialisation and ISRO’s mission areas, and questions built around your final-year project or thesis. Communication and comprehension are scored separately, so panels also probe how clearly you explain technical ideas.
How many rounds are there in the ISRO interview?
Two stages: shortlisting (on GATE score, or an ICRB written test in some cycles) and a single 100-mark Personal Interview, followed by document verification and medical. That’s a shorter pipeline than most PSUs, which often add a Group Discussion - ISRO’s SC recruitment skips that entirely; the 2025 cycle combined GATE and interview at 50:50, according to Physics Wallah.
How should I prepare for ISRO interviews?
Score well in GATE first - your rank inside the shortlisting ratio determines whether you get an interview call at all. For the interview itself, revise your GATE-syllabus subjects at depth (that’s 40 of the 100 marks), read up on ISRO’s current missions and programmes relevant to your discipline, and prepare a clear, well-rehearsed walkthrough of your final-year project since panels probe it in detail.
What GATE score or rank does ISRO require for Scientist/Engineer ‘SC’?
No fixed minimum is published - shortlisting is relative, done in roughly a 1:7 ratio of candidates to vacancies for each discipline, based on your GATE score (not raw marks or All-India Rank) in that year’s exam. The effective cutoff therefore moves every year depending on vacancy count and the applicant pool for each engineering discipline.
How to prepare for ISRO interviews
- Loop map: GATE score shortlisting; Personal Interview; Document verification & medical. Confirm timings from the drive mail.
- Technical depth: Drill the Q&A section until answers are spoken, not read. Know every resume project cold.
- Experiences: Study round-wise notes on the interview experience page - real prompts beat generic lists.
- HR: Three STAR stories + a specific “Why ISRO?” on the HR page.
Who usually fits and who struggles
Good fit: You like hard fundamentals, you will relocate to a centre, and you will put months into a written paper.
Harder path: You only grind LeetCode; you recite missions you cannot explain; you want a 25 LPA product title; you refuse every centre except one city.
A practical ISRO prep plan
Use this as a default four-week loop before a ISRO drive. Adjust to your invite timeline.
- Week 1: Language fluency: rewrite 10 old solutions in one language until you stop hunting syntax. Open the ISRO previous-year sets on this site and mark which sections ate your time. Write the timing on a sticky note. That number is more useful than a 200-problem LeetCode streak you never timed.
- Week 2: If your notification includes an ICRB written test, do three timed discipline MCQ sits this week; if you are on the GATE shortlist route, instead drill two full-length favourite-subject oral mocks with a friend acting as the panel. Log every miss: topic and why (slow, wrong formula, could not derive on the board, panic).
- Week 3: Technical interviews at ISRO usually want a clean project story, one or two CS fundamentals, and (if the process has it) a behavioral or values round. Write STAR stories on paper, not in your head. Practise “Why ISRO?” with one concrete product, lab, or business line - not a slogan.
- Week 4: Sleep, id photocopies, and a dry run of the oa platform if the invite names one. If you still have energy, redo only the questions you failed in week 2.
10-day crash version: Days 1-4 timed DSA, days 5-7 resume projects + CS fundamentals, days 8-9 mock interviews out loud, day 10 HR STAR stories on the HR page.
Compensation notes
Candidate-reported fresher/early-career packages for ISRO often cite Scientist/Engineer SC Level 10 (₹56,100 basic; ~₹8-12 LPA all-in in student notes). Treat forum numbers as ranges, not guarantees - confirm the written offer letter for your team and location.
Red flags in the ISRO loop
- Naming Chandrayaan or Gaganyaan without being able to explain one subsystem, orbit, or engineering trade-off
- Listing five “favourite subjects” then freezing on the board for the first derivation
- Treating the panel as an HR chat - most of the hour is technical fundamentals and your project
- Refusing every centre except one metro while claiming national-mission motivation
- Bluffing OS/networks/DBMS definitions; panels probe until the gap is obvious
Sources
Interview process details and sample questions on this site are editorially organized from public candidate reports and hiring write-ups, with round structure, prep notes, and company-specific framing added by our team. For round-by-round stories, see the ISRO interview experience page. For OA papers and coding drills, use ISRO on placementpapers.app. Recruitment quick answers and FAQs draw on Physics Wallah’s ISRO Scientist result page and ResultBharat’s summary of the ISRO:ICRB:01(EMC):2025 advertisement. Discipline-wise questions draw on GeeksforGeeks ISRO Scientist SC (Bengaluru, 2024) and Scientists ‘C’ (VLSI) interview experiences, ERForum’s 2017 ISRO ECE strategy post and the candidate reports compiled on our ISRO interview experience page.